Certainly on the top of many visitors' 'must see' lists, Chichén Itzá is a stunning ruin and (despite the crowds) well worth visiting for its spectacular, iconic structures, and the historical importance. It is even visible from far-away Ek' Balam. To fully take in the details you should hire a guide, but if that's not in your budget, just walking around offers insight into one of the greatest cities of the Maya world. Due to tourist injuries, climbing structures is prohibited.
At the vernal and autumnal equinoxes (around March 20 and September 22), the morning and afternoon sun produces a light-and-shadow illusion of the serpent ascending or descending the side of El Castillo’s staircase. The site is mobbed on these dates, however, making it difficult to see, and after the spectacle, parts of the site are sometimes closed to the public. The illusion is almost as good in the week preceding and following each equinox (and draws much smaller crowds), and is re-created nightly (except Mondays) in the light-and-sound show year-round. Some find the spectacle fascinating, others think it’s overrated. Either way, if you’re in the area around the equinox and you have your own car, it’s easy to wake up early for the fiery sunrise of Dzibilchaltún (a site north of Mérida) and then make it to Chichén Itzá by midafternoon, catching both spectacles on the same day.
The heat, humidity and crowds in Chichén Itzá can be fierce; try to explore the site either early in the morning or late in the afternoon. Note that the 5pm closing is a hard exit: all visitors must be through the gates well beforehand.
The 45-minute sound and light show begins each evening at 8pm in summer and 7pm in winter. You must preorder your tickets online at www.nochesdekukulkan.com. The cost is M$483 Tuesday to Saturday; M$240 Sunday.