Chichén Itzá is one of the New Seven Wonders of the World, and El Castillo is even more impressive in person than in photos. Keep in mind that it is also very busy and hot: by 11:00 the tour buses from Cancún arrive, vendors line the paths and there is little shade. Arrive at opening and it is a completely different experience.
History & How Long to Stay
Chichén Itzá was one of the largest Maya cities, at its peak between about 600 and 1200 AD. Its name means "at the mouth of the well of the Itzá", after the Sacred Cenote, where offerings (and sometimes people) were thrown to the rain god Chaac. The city mixed Maya and central Mexican (Toltec) styles. It declined in the 13th century, but pilgrims kept coming to the cenote. It became a UNESCO site in 1988 and one of the New Seven Wonders in 2007. Climbing El Castillo has been banned since 2006.
How long to stay: 3 to 4 hours at the site; stay overnight nearby or in Valladolid to arrive at opening.