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Mt. Everest has two main climbing routes, the southeast ridge from Nepal and the north ridge from Tibet, as well as many other less frequently climbed routes. Of the two main routes, the southeast ridge is technically easier and is the more frequently used route. It was the route used by Edmund Hillary and Tenzing Norgay in 1953 and the first recognized of fifteen routes to the top by 1996. This was, however, a route decision dictated more by politics than by design as the Chinese border was closed to the western world in the 1950s after the People's Republic of China invaded Tibet.

Most attempts are made during May before the summer monsoon season. As the monsoon season approaches, a change in the jet stream at this time pushes it northward, thereby reducing the average wind speeds high on the mountain. While attempts are sometimes made after the monsoons in September and October, when the jet stream is again temporarily pushed northward, the additional snow deposited by the monsoons and the less stable weather patterns (tail end of the monsoon) makes climbing extremely difficult.

Southeast ridge

Climbers will spend a couple of weeks in Base Camp, acclimatizing to the altitude. During that time, Sherpas and some expedition climbers will set up ropes and ladders in the treacherous Khumbu Icefall. Seracs, crevasses and shifting blocks of ice make the icefall one of the most dangerous sections of the route. Many climbers and Sherpas have been killed in this section. To reduce the hazard, climbers will usually begin their ascent well before dawn, when the freezing temperatures glue ice blocks in place. Above the icefall is Camp I at .

From Camp I, climbers make their way up the Western Cwm to the base of the Lhotse face, where Camp II or Advanced Base Camp (ABC) is established at . The Western Cwm is a flat, gently rising glacial valley, marked by huge lateral crevasses in the centre, which prevent direct access to the upper reaches of the Cwm. Climbers are forced to cross on the far right near the base of Nuptse to a small passageway known as the "Nuptse corner". The Western Cwm is also called the "Valley of Silence" as the topography of the area generally cuts off wind from the climbing route. The high altitude and a clear, windless day can make the Western Cwm unbearably hot for climbers.

From ABC, climbers ascend the Lhotse face on fixed ropes up to Camp III, located on a small ledge at . From there, it is another 500 meters to Camp IV on the South Col at . From Camp III to Camp IV, climbers are faced with two additional challenges: The Geneva Spur and The Yellow Band. The Geneva Spur is an anvil shaped rib of black rock named by the 1952 Swiss expedition. Fixed ropes assist climbers in scrambling over this snow covered rock band. The Yellow Band is a section of interlayered marble, phyllite, and semischist, which also requires about 100 meters of rope for traversing it.

On the South Col, climbers enter the death zone. Climbers typically only have a maximum of two or three days that they can endure at this altitude for making summit bids. Clear weather and low winds are critical factors in deciding whether to make a summit attempt. If weather does not cooperate within these short few days, climbers are forced to descend, many all the way back down to Base Camp.

From Camp IV, climbers will begin their summit push around midnight with hopes of reaching the summit (still another 1,000 meters above) within 10 to 12 hours. Climbers will first reach "The Balcony" at , a small platform where they can rest and gaze at peaks to the south and east in the early light of dawn. Continuing up the ridge, climbers are then faced with a series of imposing rock steps which usually forces them to the east into waist-deep snow, a serious avalanche hazard. At , a small table-sized dome of ice and snow marks the South Summit.

From the South Summit, climbers follow the knife-edge southeast ridge along what is known as the "Cornice traverse", where snow clings to intermittent rock. This is the most exposed section of the climb as a misstep to the left would send one 2,400 m (8,000 ft) down the southwest face, while to the immediate right is the 3,050 m (10,000 ft) Kangshung face. At the end of this traverse is an imposing 12 m (40 ft) rock wall called the "Hillary Step" at .

Hillary and Tenzing were the first climbers to ascend this step and they did it with primitive ice climbing equipment and ropes. Nowadays, climbers will ascend this step using fixed ropes previously set up by Sherpas. Once above the step, it is a comparatively easy climb to the top on moderately angled snow slopes – though the exposure on the ridge is extreme, especially while traversing large cornices of snow. With increasing numbers of people climbing the mountain in recent years, the Step has frequently become a bottleneck, with climbers forced to wait significant amounts of time for their turn on the ropes, leading to problems in getting climbers efficiently up and down the mountain. After the Hillary Step, climbers also must traverse a loose and rocky section that has a large entanglement of fixed ropes that can be troublesome in bad weather. Climbers will typically spend less than half an hour at the summit to allow time to descend to Camp IV before darkness sets in, to avoid serious problems with afternoon weather, or because supplemental oxygen tanks run out.

North ridge

''See also:'' the Three Steps

Ascents

Early expeditions

The northern approach to the mountain was discovered by George Mallory on the first expedition in 1921. It was an exploratory expedition not equipped for a serious attempt to climb the mountain. With Mallory leading (and thus becoming the first European to set foot on Everest's flanks) they climbed the North Col . From there, Mallory espied a route to the top, but the party was unprepared for the great task of climbing any further and descended.

The British returned for a 1922 expedition. George Finch ("The other George") climbed using oxygen for the first time. He ascended at a remarkable speed— per hour, and reached an altitude of , the first time a human climbed higher than 8,000m. This feat was entirely lost on the British climbing establishment—except for its "unsporting" nature. Mallory and Col. Felix Norton made a second unsuccessful attempt. Mallory was faulted for leading a group down from the North Col which got caught in an avalanche. Mallory was pulled down too, but seven native porters were killed.

The next Expedition was in 1924. The initial attempt by Mallory and Bruce was aborted when weather conditions precluded the establishment of Camp VI. The next attempt was that of Norton and Somervell, who climbed without oxygen and in perfect weather, traversing the North Face into the Great Couloir. Norton managed to reach , though he ascended only or so in the last hour. Mallory rustled up oxygen equipment for a last-ditch effort. He chose young Andrew Irvine as his partner.

On 8 June 1924, George Mallory and Andrew Irvine made an attempt on the summit via the North Col/North Ridge/Northeast Ridge route from which they never returned. On 1 May 1999, the Mallory and Irvine Research Expedition found Mallory's body on the North Face in a snow basin below and to the west of the traditional site of Camp VI. Controversy has raged in the mountaineering community whether one or both of them reached the summit 29 years before the confirmed ascent (and of course, safe descent) of Everest by Sir Edmund Hillary and Tenzing Norgay in 1953.

In 1933, Lady Houston, a British millionairess, funded the ''Houston Everest Flight of 1933'', which saw a formation of aircraft led by the Marquess of Clydesdale fly over the summit in an effort to deploy the British Union Flag at the top.

Early expeditions—such as Bruce's in the 1920s and Hugh Ruttledge's two unsuccessful attempts in 1933 and 1936—tried to make an ascent of the mountain from Tibet, via the north face. Access was closed from the north to western expeditions in 1950, after the Chinese asserted control over Tibet. In 1950, Bill Tilman and a small party which included Charles Houston, Oscar Houston and Betsy Cowles undertook an exploratory expedition to Everest through Nepal along the route which has now become the standard approach to Everest from the south.

The Swiss expedition of 1952, led by Edouard Wyss-Dunant, was granted permission to attempt a climb from Nepal. The expedition established a route through the Khumbu ice fall and ascended to the South Col at an elevation of . No attempt at an ascent of Everest was ever under consideration in this case. Raymond Lambert and Sherpa Tenzing Norgay were able to reach a height of about on the southeast ridge, setting a new climbing altitude record. Tenzing's experience was useful when he was hired to be part of the British expedition in 1953.

First successful ascent by Tenzing and Hillary

News of the expedition's success reached London on the morning of Queen Elizabeth II's coronation, 2 June. Returning to Kathmandu a few days later, Hunt (a Briton) and Hillary (a New Zealander) discovered that they had been promptly knighted in the Order of the British Empire, a KBE, for the ascent. Tenzing, a Nepali sherpa who was a citizen of India, was granted the George Medal by the UK. Hunt was ultimately made a life peer in Britain, while Hillary became a founding member of the Order of New Zealand. Hillary and Tenzing are also nationally recognized in Nepal, where annual ceremonies in schools and offices celebrate their accomplishment.

Records broken

;First female ascent The first woman to get to the top was Junko Tabei, in 1975, after being rescued from an avalanche by her sherpa.

;First ascents without supplemental oxygen and first solo ascent On 8 May 1978, Reinhold Messner (Italy) and Peter Habeler (Austria) made the first ascent without supplemental oxygen, using the southeast ridge route.

On 20 August 1980, Messner reached the summit of the mountain solo for the first time, without supplementary oxygen or support, on the more difficult Northwest route via the North Col to the North Face and the Great Couloir. He climbed for three days entirely alone from his base camp at .

;First winter ascent In 1980, a team from Poland led by Andrzej Zawada, Leszek Cichy, and Krzysztof Wielicki became the first to reach the summit during the winter season.

;First ascent from sea level In 1990 Australian Tim Macartney-Snape became the first person to climb from sea level to the summit.

1996 disaster

Journalist Jon Krakauer, on assignment from ''Outside'' magazine, was in one of the affected parties, and afterwards published the bestseller ''Into Thin Air'', which related his experience. Anatoli Boukreev, a guide who felt impugned by Krakauer's book, co-authored a rebuttal book called ''The Climb.'' The dispute sparked a debate within the climbing community. In May 2004, Kent Moore, a physicist, and John L. Semple, a surgeon, both researchers from the University of Toronto, told ''New Scientist'' magazine that an analysis of weather conditions on 11 May suggested that freak weather caused oxygen levels to plunge approximately 14%.

The storm's impact on climbers on the North Ridge of Mount Everest, where several climbers also died, was detailed in a first-hand account by British filmmaker and writer Matt Dickinson in his book ''The Other Side of Everest''. 16-year-old Mark Pfetzer was on the climb and wrote about it in his account, ''Within Reach: My Everest Story''.

2005: Helicopter landing

Some press reports suggested that the report of the summit landing was a misunderstanding of a South Col landing, but he had also landed on South Col two days earlier, with this landing and the Everest records confirmed by the Fédération Aéronautique Internationale. Delsalle also rescued two Japanese climbers at 16,000 feet (4,877 meters) while he was there. One climber noted that the new record meant a better chance of rescue.

2006: Controversy

As this debate raged, on 26 May, Australian climber Lincoln Hall was found alive, after being declared dead the day before. He was found by a party of four climbers (Dan Mazur, Andrew Brash, Myles Osborne and Jangbu Sherpa) who, giving up their own summit attempt, stayed with Hall and descended with him and a party of 11 Sherpas sent up to carry him down. Hall later fully recovered. Similar actions have been recorded since, including on 21 May 2007, when Canadian climber Meagan McGrath initiated the successful high-altitude rescue of Nepali Usha Bista. Recognizing her heroic rescue, Major Meagan McGrath was selected as a 2011 recipient of the Sir Edmund Hillary Foundation of Canada Humanitarian Award, which recognizes a Canadian who has personally or administratively contributed a significant service or act in the Himalayan Region of Nepal.

2010

The youngest person to climb Mount Everest was 13-year-old Jordan Romero in May 2010 from the Tibetan side. His ascent, as part of an apparent "race" to bring younger and younger children to the mountain (shortly after Romero's ascent, Pemba Dorjie Sherpa announced plans to bring his 9 year old son to the summit), triggered a wave of criticism that prompted Chinese authorities to establish age limits on Mt Everest. At the present time, China no longer grants permits to prospective climbers under 18 or over 60. Nepal sets the minimum age at 16 but has no maximum age.

Various records

Apa Sherpa holds the record for reaching the summit more times than any other person, 21 times as of 2011.

The first descent by paraglider was by Jean-Marc Boivin on 26 September 1988 and the first full descent by ski was in 2000 by Davo Karnicar.

The oldest climber to reach Mount Everest's summit is 76-year-old Min Bahadur Sherchan, on 25 May 2008 from the Nepalese side. Sherchan beat the previous record set in 2007 by 71-year-old Katsusuke Yanagisawa. The oldest climber to reach the summit of Mount Everest from both sides (Nepal and Tibet) of the mountain is 60-year-old Julio Bird, a Puerto Rican cardiologist who reached the summit of Mount Everest from the north side on 17 May 2010.

The first self-propelled ascent of Mount Everest, the highest point on the earth's surface, starting from the lowest point on the earth's surface – the Dead Sea – was by Phil and Pauline Sanderson in 2006.

Mt. Everest Speed Climbing Records

Southeast Ridge (South Col)

Statistics

By the end of the 2010 climbing season, there had been 5,104 ascents to the summit by about 3,142 individuals. 80% of these ascents took place since 2000. In 2007, the record number of 633 ascents has been recorded, by 350 climbers and 253 sherpas.

A remarkable illustration of the explosion of popularity of Everest is provided by the numbers of daily ascents. As mentioned below, the 1996 disaster was partly blamed on the number of climbers (33 to 36) attempting to summit on the same day; this was considered unusually high at the time. By comparison, on May 23, 2010, the summit of Mount Everest was reached by 169 climbers.

Nearly all attempts at the summit are done using one of the two main routes. The traffic seen by each route varies from year to year. In 2005-07, more than half of all climbers elected to use the more challenging, but cheaper northeast route. In 2008, the northeast route was closed by the Chinese government for entire climbing season, and the only people able to reach the summit from the north that year were athletes responsible for carrying the Olympic torch for the 2008 Summer Olympics. The route was closed to foreigners once again in 2009 in the run-up to the 50th anniversary of the Dalai Lama's exile. These closures led to declining interest in the north route, and, in 2010, two thirds of the climbers reached the summit from the south.

There were 219 fatalities recorded on Mount Everest since the 1922 British Mount Everest Expedition through the end of 2010. 54 of these occurred after 2000: 33 on the northeast ridge, 17 on the southeast ridge, 2 on southwest face, and 2 on north face.

Everest economy

Beyond this point, costs may vary widely. It is technically possible to reach the summit with minimal additional expenses, and there are 'budget' travel agencies which offer logistical support for such trips. However, this is considered difficult and dangerous (as illustrated by the case of David Sharp). Many climbers hire "full service" guide companies, which provide a wide spectrum of services, including acquisition of permits, transportation to/from base camp, food, tents, fixed ropes, medical assistance while on the mountain, an experienced mountaineer guide, and even personal porters to carry one's backpack and cook one's meals. The cost of such a guide service may range from $40,000 to $80,000 per person. Since most equipment is moved by sherpas, clients of full-service guide companies can often keep their backpack weights under , or hire a sherpa to carry their backpack for them. This can be contrasted with expeditions to less commercialized peaks (for example, climbers attempting Mount McKinley are often expected to carry backpacks over and occasionally to tow a sled with of gear and food.)

According to Jon Krakauer, the era of commercialization of Everest started in 1985, when the summit was reached by a guided expedition led by David Breashears that included Richard Bass, a wealthy 55 year old businessman and an amateur mountain climber with only 4 years of climbing experience. By the early 1990s, multiple companies were offering guided tours to the mountain. Rob Hall, the mountaineer who died in the 1996 disaster, had successfully guided 39 clients to the summit prior to that incident.

The degree of commercialization of Mount Everest is a frequent subject of criticism. Jamling Tenzing Norgay, the son of Tenzing Norgay, said in a 2003 interview that his late father would have been shocked to discover that rich thrill-seekers with no climbing experience were now routinely reaching the summit:

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Reinhold Messner concurred in 2004:

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However, not all opinions on the subject among prominent mountaineers are strictly negative. For example, Edmund Hillary, who went on record saying that he hasn't liked "the commercialization of mountaineering, particularly of Mt. Everest" and claimed that "Having people pay $65,000 and then be led up the mountain by a couple of experienced guides ... isn't really mountaineering at all", nevertheless noted that he was pleased by the changes brought to Everest area by the Westerners:

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Rescues

Death zone

Another significant threat to climbers is low atmospheric pressure. The atmospheric pressure at the top of Everest is about a third of sea level pressure or , resulting in the availability of only about a third as much oxygen to breathe.

Debilitating effects of the death zone are so great that it takes most climbers up to 12 hours to walk the distance of ) from South Col to the summit. Achieving even this level of performance requires prolonged altitude acclimatization, which takes 40–60 days for a typical expedition. A sea-level dweller exposed to the atmospheric conditions at the altitude above without acclimatization would likely lose consciousness within 2 to 3 minutes.

In May 2007, the Caudwell Xtreme Everest undertook a medical study of oxygen levels in human blood at extreme altitude. Over 200 volunteers climbed to Everest Base Camp where various medical tests were performed to examine blood oxygen levels. A small team also performed tests on the way to the summit.

Even at base camp, the low partial pressure of oxygen had direct effect on blood oxygen saturation levels. At sea level, blood oxygen saturation is generally 98% to 99%. At base camp, blood saturation fell to between 85% and 87%. Blood samples taken at the summit indicated very low oxygen levels in the blood. A side effect of low blood oxygen is a vastly increased breathing rate, often 80–90 breaths per minute as opposed to a more typical 20–30. Exhaustion can occur merely attempting to breathe.

Lack of oxygen, exhaustion, extreme cold, and climbing hazards all contribute to the death toll. An injured person who cannot walk is in serious trouble, since rescue by helicopter is generally impractical and carrying the person off the mountain is very risky. People who die during the climb are typically left behind. About 150 bodies have never been recovered. It is not uncommon to find corpses near the standard climbing routes.

Supplemental oxygen

Most expeditions use oxygen masks and tanks above . Everest can be climbed without supplementary oxygen, but only by the most accomplished mountaineers and at increased risk. Humans do not think clearly with low oxygen, and the combination of extreme weather, low temperatures, and steep slopes often require quick, accurate decisions.

The use of bottled oxygen to ascend Mount Everest has been controversial. It was first used in 1922 by George Finch ("the other George") and Geoffrey Bruce who climbed up to at a spectacular speed of 1000 vertical feet per hour. Pinned down by a fierce storm, they escaped death by breathing oxygen from a jury-rigged set-up during the night. The next day they climbed to at 900 vf/h – nearly three times as fast as non-oxygen users. Yet the use of oxygen was considered so unsportsmanlike that none of the rest of the Alpine world recognized this high ascent rate. George Mallory himself described the use of such oxygen as unsportsmanlike, but he later concluded that it would be impossible for him to summit without it and consequently used it in his ill-fated attempt in 1924. When Tenzing and Hillary made the first successful summit in 1953, they used bottled oxygen. For the next twenty-five years, bottled oxygen was considered standard for any successful summit.

Reinhold Messner was the first climber to break the bottled oxygen tradition and in 1978, with Peter Habeler, made the first successful climb without it. Although critics alleged that he sucked mini-bottles of oxygen – a claim that Messner denied – Messner silenced them when he summited the mountain solo, without supplemental oxygen or any porters or climbing partners, on the more difficult northwest route, in 1980. Once the climbing community was satisfied that the mountain could be climbed without supplemental oxygen, many purists then took the next logical step of insisting that's how it ''should'' be climbed.

The aftermath of the 1996 disaster further intensified the debate. Jon Krakauer's ''Into Thin Air'' (1997) expressed the author's personal criticisms of the use of bottled oxygen. Krakauer wrote that the use of bottled oxygen allowed otherwise unqualified climbers to attempt to summit, leading to dangerous situations and more deaths. The 10–11 May 1996 disaster was partially caused by the sheer number of climbers (34 on that day) attempting to ascend, causing bottlenecks at the Hillary Step and delaying many climbers, most of whom summitted after the usual 2 p.m. turnaround time. He proposed banning bottled oxygen except for emergency cases, arguing that this would both decrease the growing pollution on Everest—many bottles have accumulated on its slopes—and keep marginally qualified climbers off the mountain.

The 1996 disaster also introduced the issue of the guide's role in using bottled oxygen. Guide Anatoli Boukreev's decision not to use bottled oxygen was sharply criticized by Jon Krakauer. Boukreev's supporters (who include G. Weston DeWalt, who co-wrote ''The Climb'') state that using bottled oxygen gives a false sense of security. Krakauer and his supporters point out that, without bottled oxygen, Boukreev could not directly help his clients descend. They state that Boukreev said that he was going down with client Martin Adams, but just below the South Summit, Boukreev determines that Adams was doing fine on the descent and so descends at a faster pace, leaving Adams behind. Adams states in ''The Climb'': "For me, it was business as usual, Anatoli's going by, and I had no problems with that."

Thefts and other crimes

In addition to theft, the 2008 book ''High Crimes'' by Michael Kodas describes unethical guides and Sherpas, prostitution and gambling at the Tibet Base Camp, fraud related to the sale of oxygen bottles, and climbers collecting donations under the pretense of removing trash from the mountain.

Flora and fauna

Geology

Geologists have subdivided the rocks comprising Mount Everest into three units called "formations". Each formation is separated from the other by low-angle faults, called “detachments”, along which they have been thrust over each other. From the summit of Mount Everest to its base these rock units are the Qomolangma Formation, the North Col Formation, and the Rongbuk Formation.

From its summit to the top of the Yellow Band, about 8,600 m (28,000 ft) above sea level, the top of Mount Everest consists of the Qomolangma Formation, which has also been designated as either the Everest Formation or Jolmo Lungama Formation. It consists of grayish to dark gray or white, parallel laminated and bedded, Ordovician limestone inter layered with subordinate beds of recrystallized dolomite with argillaceous laminae and siltstone. Gansser first reported finding microscopic fragments of crinoids in this limestone. Later petrographic analysis of samples of the limestone from near the summit revealed them to be composed of carbonate pellets and finely fragmented remains of trilobites, crinoids, and ostracods. Other samples were so badly sheared and recrystallized that their original constituents could not be determined. A thick, white-weathering thrombolite bed that is 60 m (200 ft) thick comprises the foot of the "Third Step," and base of the summit pyramid of Everest. This bed, which crops out starting about 70 m (300 ft) below the summit of Mount Everest, consists of sediments trapped, bound, and cemented by the biofilms of microorganisms, especially cyanobacteria, in shallow marine waters. The Qomolangma Formation is broken up by several high-angle faults that terminate at the low angle thrust fault, the Qomolangma Detachment. This detachment separates it from the underlying Yellow Band. The lower five meters of the Qomolangma Formation overlying this detachment are very highly deformed.

The bulk of Mount Everest, between 7,000 and 8,600 m (23,000 and 28,200 ft), consists of the North Col Formation, of which the Yellow Band forms its upper part between 8,200 to 8,600 m (26,900 to 28,200 ft). The Yellow Band consists of intercalated beds of Middle Cambrian diopside-epidote-bearing marble, which weathers a distinctive yellowish brown, and muscovite-biotite phyllite and semischist. Petrographic analysis of marble collected from about 8,300 m (27,200 ft) found it to consist as much as five percent of the ghosts of recrystallized crinoid ossicles. The upper five meters of the Yellow Band lying adjacent to the Qomolangma Detachment is badly deformed. A 5–40 cm (2–16 in) thick fault breccia separates it from the overlying Qomolangma Formation.

The remainder of the North Col Formation, exposed between 7,000 to 8,200 m (23,000 to 26,900 ft) on Mount Everest, consists of interlayered and deformed schist, phyllite, and minor marble. Between 7,600 and 8,200 m (24,900 and 26,900 ft), the North Col Formation consists chiefly of biotite-quartz phyllite and chlorite-biotite phyllite intercalated with minor amounts of biotite-sericite-quartz schist. Between 7,000 and 7,600 m (23,000 and 24,900 ft), the lower part of the North Col Formation consists of biotite-quartz schist intercalated with epidote-quartz schist, biotite-calcite-quartz schist, and thin layers of quartzose marble. These metamorphic rocks appear to be the result of the metamorphism of Middle to Early Cambrian deep sea flysch composed of interbedded, mudstone, shale, clayey sandstone, calcareous sandstone, graywacke, and sandy limestone. The base of the North Col Formation is a regional thrust fault called the "Lhotse detachment".

Below 7,000 m (23,000 ft), the Rongbuk Formation underlies the North Col Formation and forms the base of Mount Everest. It consists of sillimanite-K-feldspar grade schist and gneiss intruded by numerous sills and dikes of leucogranite ranging in thickness from 1 cm to 1,500 m (0.4 in to 4,900 ft).

Environment

In 2008, a new weather station at about 8000 m altitude (26,246 feet) went online. The station's first data in May 2008 was air temperature -17 °C, relative humidity 41.3 %, atmospheric pressure 382.1 hPa (38.21 kPa), wind direction 262.8°, wind speed 12.8 m/s (28.6 mph), global solar radiation 711.9 watts/m², solar UVA radiation 30.4 W/m². The project was orchestrated by Stations at High Altitude for Research on the Environment (SHARE), who also placed the Mount Everest webcam in 2011. The weather station is located on the South Col and is solar powered.

See also

References

Further reading

External links

Category:China–Nepal border Category:Eight-thousanders Category:Extreme points of Earth Category:Himalayas Category:International mountains of Asia Category:Mountains of China Category:Mountains of Nepal Category:Mountains of Tibet Category:Sacred mountains Category:Seven Summits Category:Shigatse Prefecture Category:Visitor attractions in Tibet