Directly north of (ie behind) Haghia Sophia are the walls shielding the imperial enclave of Topkapý Palace. Part command centre for a massive military empire, part archetypal Eastern pleasure dome, the palace was the hub of Ottoman power for more than three centuries, until it was superseded by the Dolmabahçe Palace in 1853. In terms of lavish decor and exquisite siting, it rivals Granada's Alhambra and beats hands down almost anything else in Europe. At least half a day is needed to explore the place fully, although given the high admissions you might want to take a full day over it to get your money's worth. If pushed for time, the must-see elements are the Harem, Imperial Treasury and the views from the fourth and innermost courtyard. Entrance is via the Imperial Gate (Bab-i Hümayun), erected by the Sultan Fatih in 1478 and decorated with niches that during Ottoman times were used to display the severed heads of rebels and criminals. The gate leads into the first of a series of four courts that become more private the deeper into the complex you penetrate. The First Court was public and not considered part of the palace proper. It housed a hospital and dormitories for the palace guards, hence the popular name, Court of the Janissaries. Off to the left is the church of Haghia Irene (Aya Irini Kilisesi), built by Justinian and thus a contemporary of Haghia Sophia. It has the distinction of being the only pre-Ottoman-conquest church in the city that was never turned into a mosque. Closed most of the time, the church serves as a concert venue during the International Istanbul Music Festival. Still in the First Court, down the hill to the left, is the superb Archaeological Museum, but the palace proper is entered through the Disneyesque gate ahead. Tickets can be bought on the right, just before you reach the gate, beside the Executioner's Fountain, where the chief axeman washed his blade after carrying out his grisly work. The heads of his victims were also displayed on top of the truncated columns that stand on either side of the fountain. A semi-public space, the enormous Second Court is where the business of running the empire was carried out. This is where the viziers of the imperial council sat in session in the divan, overlooking gardens landscaped with cypresses, plane trees and rose bushes. Where once there would have been crowds of petitioners awaiting their turn for an audience, nowadays there are queues lined up waiting to get in to the Harem , an introverted complex of around 300 brilliantly tiled chambers on several levels, connected by arcaded courts and fountain gardens. Unfortunately, access is severely limited: you must wait to join a group that leaves every half-hour and is led through no more than a dozen chambers by an official guide. It's not the ideal way to see the place - locked in a crowd and herded around - but it's the only way. Tickets are sold separately, from a window located beside the Harem entrance. Around from the Harem ticket window, a low brick building topped by shallow domes is the former State Treasury, present home of an exhibition of arms and armour, interesting for the contrast between cumbersome, bludgeonly European swords and the lighter, more deadly-looking Ottoman model. Across the gardens, a long row of ventilation chimneys punctuates the roof line of the enormous kitchens, which catered for up to 5,000 inhabitants of the palace. They now contain a collection of ceramics, glass and silverware, much of it originating from China and Japan and imported via Central Asia along the legendary Silk Route. The earliest pieces are Chinese celadon, particularly valued by the sultans because it was supposed to change colour when brought into contact with poison. All paths in the Second Court converge on the Gate of Felicity (Bab-üs Saadet), which serves as the backdrop every year for a performance of Mozart's Abduction From the Seraglio - again, part of the International Istanbul Music Festival. The gate also gives access to the Third Court. The Third Court was the holy of holies, the sultan's private domain. Confronting all who enter is the Audience Chamber (Arz Odasý), which is where, until it was supplanted in the role by the Sublime Porte , foreign ambassadors would present their credentials. Although the sultan would be present on such occasions, he would never deign to speak with a non-Turk and all conversation was conducted via the grand vizier. Off to the right is the Hall of the Campaign Pages (Seferli Koðuþu), whose task it was to look after the royal wardrobe. They did an excellent job: there's a perfectly preserved 550-year-old, red-and-gold silk kaftan worn by Mehmet II, conqueror of Constantinople. Things get even more glittery next door in the Imperial Treasury (Hazine). Many of the items here were made specifically for the palace by a team of court artisans, which at its height numbered over 600. A lot of what's displayed here has never left

Hagia Sophia (from the Greek: Ἁγία Σοφία, "Holy Wisdom"; Latin: Sancta Sophia or Sancta Sapientia; Turkish: Aya Sofya) is a former Orthodox patriarchal basilica, later a mosque, and now a museum in Istanbul, Turkey. From the date of its dedication in 360 until 1453, it served as the cathedral of Constantinople, except between 1204 and 1261, when it was converted to a Roman Catholic cathedral under the Latin Patriarch of Constantinople of the Western Crusader established Latin Empire. The building was a mosque from 29 May 1453 until 1934, when it was secularized. It was opened as a museum on 1 February 1935.[1] The Church was dedicated to the Logos, the second person of the Holy Trinity,[2] its dedication feast taking place on December 25, the anniversary of the incarnation of the Logos in Christ.[2] Although it is sometimes referred to as Sancta Sophia (as though it were named after Saint Sophia), sophia is the phonetic spelling in Latin of the Greek word for wisdom - the full name in Greek being Ναός τῆς Ἁγίας τοῦ Θεοῦ Σοφίας, "Church of the Holy Wisdom of God".[3][4] Famous in particular for its massive dome, it is considered the epitome of Byzantine architecture and is said to have "changed the history of architecture."[5] It was the largest cathedral in the world for nearly a thousand years, until Seville Cathedral was completed in 1520. The current building was originally constructed as a church between 532 and 537 on the orders of the Byzantine Emperor Justinian and was the third Church of the Holy Wisdom to occupy the site, the previous two having both been destroyed by rioters. It was designed by Isidore of Miletus, a physicist, and Anthemius of Tralles, a mathematician.[6] The church contained a large collection of holy relics and featured, among other things, a 49 foot (15 m) silver iconostasis. It was the seat of the Patriarch of Constantinople and the religious focal point of the Eastern Orthodox Church for nearly one thousand years. It is the church in which Cardinal Humbert in 1054 excommunicated Michael I Cerularius - which is commonly considered the start of the Great Schism. In 1453, Constantinople was conquered by the Ottoman Turks under Sultan Mehmed II, who subsequently ordered the building converted into a mosque.[7] The bells, altar, iconostasis, and sacrificial vessels were removed and many of the mosaics were plastered over. Islamic features — such as the mihrab, minbar, and four minarets — were added while in the possession of the Ottomans. It remained a mosque until 1935, when it was converted into a museum by the Republic of Turkey. For almost 500 years the principal mosque of Istanbul, Hagia Sophia served as a model for many other Ottoman mosques, such as the Sultan Ahmed Mosque (Blue Mosque of Istanbul), the Şehzade Mosque, the Süleymaniye Mosque, the Rüstem Pasha Mosque and the Kılıç Ali Paşa Mosque.