For the Inca trail related to Machu Picchu, see Intipuncu.

The Gate of the Sun is a megalithic solid stone arch or gateway constructed by the ancient Tiwanaku culture of Bolivia over 1500 years before the present.

It is located near Lake Titicaca at about 3,825 m above sea level near La Paz, Bolivia. The object is approximately 9.8 ft (3.0 m) tall and 13 ft (4.0 m) wide, and is constructed from a single piece of stone. The weight is estimated to be 10 tons. When rediscovered by European explorers in the mid-19th century, the megalith was lying horizontally and had a large crack going through it. It currently stands in the same location where it was found, although it is believed that this is not its original location, which remains uncertain.

The Gate of the Sun is a valuable monument to the history of art and ancient architecture. Some elements of Tiwanaku iconography spread throughout Peru and parts of Bolivia. Although there have been various modern interpretations of the mysterious inscriptions found on the object, the engravings that decorate the gate are believed to possess astronomical and/or astrological significance and may have served a calendrical purpose.

The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,000 km, about 109 times that of Earth, and its mass (about 2×10³⁰ kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,628 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others.

The Sun's stellar classification, based on spectral class, is G2V, and is informally designated as a yellow dwarf, because its visible radiation is most intense in the yellow-green portion of the spectrum and although its color is white, from the surface of the Earth it may appear yellow because of atmospheric scattering of blue light. In the spectral class label, G2 indicates its surface temperature of approximately 5778 K (5505 °C), and V indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen each second. Once regarded by astronomers as a small and relatively insignificant star, the Sun is now thought to be brighter than about 85% of the stars in the Milky Way galaxy, most of which are red dwarfs. The absolute magnitude of the Sun is +4.83; however, as the star closest to Earth, the Sun is the brightest object in the sky with an apparent magnitude of −26.74. The Sun's hot corona continuously expands in space creating the solar wind, a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.