CHICHEN ITZA, Mexico -- If there's one day trip you should take while visiting the Yucatan, it's to Chichen Itza.

Two years ago last week, the main pyramid of this ancient Mayan city was declared one of the New Seven Wonders of the World in a worldwide vote involving more than 100 million people.

Its selection was announced by the New7Wonders Foundation on July 7, 2007 -- 07/07/07 -- and also included China's Great Wall, Petra in Jordan, Christ Redeemer statue in Brazil, Machu Picchu in Peru, the Colosseum in Rome and the Taj Mahal in India. An honorary eighth wonder was the Giza pyramids in Egypt, which were part of the original Seven Ancient Wonders of the World.

Because it's just two hours west of Cancun, the six-square-mile area of Chichen Itza is one of the most visited of the Mayan sites. Although many of the temples have been excavated from the thick jungle over just the past few decades, they're no less impressive than the pyramids of ancient Egypt. The beginning of the city stretches back as early as A.D. 550 to 800.

The focal point of Chichen Itza is the 75-foot-tall Temple of Kukulkan, also known as El Castillo, or the castle. The Mayas, which invented the concept of zero, also mastered astrology. They created the temple as a physical calendar aligned with the sun. It's designed with such perfection that in the late afternoon on the spring and autumn equinoxes, the sun casts shadows depicting the plumes of a serpent that slithers down the steps. The creature's body eventually links with the stone serpent's head at the bottom of one of the staircases.

Chichen Itza also contains the largest ball court of any discovered sites. The court is so acoustically perfect that if you clap loudly seven times, it will echo back seven times.

Unfortunately, because of some serious falls that occurred among visitors who climbed the pyramids, they've been off limits to tourists for the past 2 1/2 years.

It takes about two hours to explore the high points and it's best seen with a guide who can explain the history and many of the site's architectural features. If you like ghoulish stuff, don't miss the Temple of Skulls.

Because you're inland, it can be very hot at the ruins, so bring water, a hat and good walking shoes.

Most tours of Chichen Itza include a stop at one of the cenotes -- underground lakes that have formed where a river breaks through the limestone surface. You walk down steps that descend deep into the earth to find a large cavern with high ceilings. The water is chilly (but feels good after a hot day walking around the ruins), and swimming is a little eerie because you can't feel the bottom. There's a small hole at the top of the cavern that brings in a shaft of daylight. Up above, bats sweep across the ceiling.

Local hotels can book tours to Chichen Itza, or you can explore on your own if you've rented a car. The bus tours generally cost $77 to $110 apiece (the more expensive includes a continental breakfast). Both include a hearty lunch at the opulent Hotel & Bungalows Mayaland (985-851-0127; www.mayaland.com) just outside the entrance to Chichen Itza, where you can watch dancers in costume balance trays of beer on their heads.

It's so close to the ruins that from the hotel's front door you can see the impressive El Caracol, the large observatory at Chichen Itza.