Chichén Itzá is a world-famous archaeological site that was once one of the most important Mayan cities. Today it is a UNESCO World Heritage Site and one of the most visited travel sights in Mexico. With its first settlers dating back to 550, Chichén Itzá became a religious, military, political, and commercial center that at its peak was home to 35,000 people. A massive Chichén Itzá Pyramid (or El Castillo or Temple of Kukulcan) is the most astonishing Mayan ruin inside the archaeological site. El Castillo has also recently become one of the New Seven Wonders of the World, making it quite popular among tourists. So we recommend arriving as early in the day as possible to avoid crowds (doors open at 8:00 am).