Mexico

The most famous and best restored of the region's Mayan sites, Chichén Itzá (Mouth of the Well of the Itzáes) is breathtaking. Other than a few minor passageways, El Castillo is now the only structure you can climb or enter. At the vernal and autumnal equinoxes, the morning and afternoon sun produce the illusion of a serpent along the side of the 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 in the light-and-sound show year-round.

Some find the spectacle fascinating, others think it's over-rated. Either way, if you're here around the equinox and you've got your own car it's easy to wake up early for Dzibilchaltún's fiery sunrise and then make it to Chichén Itzá by mid-afternoon, catching both spectacles on the same day.

The heat, humidity and crowds can be fierce; try to do your exploration of the site (especially climbing El Castillo) either early in the morning or late in the afternoon.