The central plaza that separates the religious from the urban section, has a great rock in the center. The religious section contains splendid architecture an masonry work, one of the most important and enigmatic is probably the Intihuatana shrine, this block of granite was presumably used to make astronomical observations. Next to this structure is another three walled building, known as the 'Temple of the Three Windows', so called because of the trapezoidal openings on the east wall. Directly across is the Royal sector, with ample buildings typical of Inca royalty. Its base forms a cavern known as the Royal Tomb.
Recent studies show that the actual purpose was for astronomical observance.
The Temple of the Moon', located halfway down in an underground chamber on the north side of the Huayna Picchu, is a fairly recent discovery. The access to this site is rather difficult and diverges left from the main trail. It contains finely carved structures on large boulders. The climb to the top takes about three hours. The citadel is a stupendous achievement- in urban planning, civil engineering, architecture and stonemasonry.