The most famous and best restored of the Yucatán Maya sites, Chichén Itzá, while tremendously overcrowded – every gawker and his or her grandmother is trying to check off the new seven wonders of the world – will still impress even the most jaded visitor. Yes, it's goosebump material. Many mysteries of the Maya astronomical calendar are made clear when one understands the design of the ‘time temples’ here. Other than a few minor passageways, climbing on the structures is not allowed.
The heat, humidity and crowds in Chichén Itzá can be fierce, as can competition between the craft sellers who line the paths (not to mention the irritating habit of hordes clapping to illustrate the pyramid acoustics). To avoid this, try to explore the site either early in the morning or late in the afternoon.
A nightly sound and light show gets some people fired up; others less so.