A Sacred Underworld

Where: Maya Riviera, Mexico

The many cenotes (canyons or sinkholes) running along the Maya Riviera have quite a history. Carved out of the Yucatán Peninsula's limestone surface, their pools of water sustained ancient cultures including the Mayans, who revered them as sacred places. It's easy to see why.

As you approach a cenote's cool cavernous opening, you'll see jagged edges caused by years of erosion, often overgrown with trees and other jungle vegetation. Bats hang overhead. Narrow streaks of light slip through the small hole above as you plunge into the crystal clear, calm water. After you submerge, your eyes slowly adjust to the darkness (or you turn on your dive light), and countless bizarre stalactites -- in the shape of columns, icicles, and chandeliers -- come into view. Small fish glide between your legs. As you descend further and explore this strange subterranean place, it's like entering another world.

Although it may be tempting to go even deeper, there are strict rules about who can dive where in this maze-like environment. Guidelines on standards and certifications differentiate a cenote from a cave. In the diving context, a cenote is defined as an area where there is visible light every 60m (200 ft.), while a cave extends beyond those dimensions. To explore a cenote as a certified open-water diver, you must go with a cave-certified guide. The only divers permitted to enter cave systems are certified cave divers, who have the skills and understand the safety procedures for this type of technical diving. If you're determined to go further than cenotes and dive in the caves, specialized certification courses are offered at the Cenote Dive Center (see below) in Tulum. This is also a good place to base yourself for other watersports, as well as remarkable ruins and hiking opportunities.

If you're not a scuba aficionado, you can swim and snorkel in some cenotes. And for most diving enthusiasts, these natural wonders offer more than enough adventure, so don't feel pressured to head for the caves. Cenotes are unique to this part of the world, and no two are exactly alike. The moon-shaped Gran Cenote is famous for its surreal mineral deposits and fantastic visibility. Calvera (Temple of Doom) includes three sinkholes filled with a mixture of fresh and salt water called halocline. Dos Ojos (Two Eyes) is connected to the larger Nohoch Nah Chich cave system. Caverna de Murcielagos (Bat Cave) is a gallery of contrasts, with huge columns and smaller intricate rock formations. Whichever ones you delve into, you won't be disappointed.

Information: Mexico Tourism Board, Calle 28 Mza. 4 Lote 1 Col. Ejidal, Playa del Carmen (tel. 52/984-206-3150; www.visitmexico.com and www.rivieramaya.com).

Travel Providers: Cenote Dive Center, Carretara Cancun-Tulum, across from the HSBC bank (tel. 52/984-871-2232; www.cenotedive.com). Hidden Worlds, Highway 307 (tel. 52/984-877-8535; www.hiddenworlds.com).

When to Go: Nov-Apr.

Getting There: Cancun airport.

Where to Stay: Ana y Jose Charming Hotel, Carretera Cancun-Tulum Bocapaila Km. 7, Tulum (tel. 52/998-880-5629; www.anayjose.com).