In Yucatan, a Theme Park of Natural Wonders : A Mexican businessman is planning a 250-acre adventure resort with an underground river and Mayan ruins.

Miguel Quintana-Pali is lost, caught in the vegetable grip of the Mexican jungle. A lacy scrim of palms fragments the sky. Roots twine underfoot. Ahead, a riot of green blocks the way. There’s not a trail in sight. The cicadas are whirring. Which way to turn?

“I’m looking for the entrance to the botanical garden,” says a puzzled Quintana.

Forgive the seemingly addled architect, entrepreneur and millionaire owner of a string of furniture stores. He has not been out in the sun too long. And he’s got a right to be confused. After all, he’s got a lot on his mind.

Here on the eastern coast of the Yucatan Peninsula, Quintana is building a 250-acre ecological theme park that he calls Xcaret (shkar-ET). The construction budget is as bottomless as the cenotes, or limestone sinkholes, that dot his domain. Quintana has already dropped $10 million into the project, and figures he’ll need $16 million more.

The size of Epcot Center in Orlando, Fla., Xcaret is composed of equal parts Tarzan, Huck Finn and Mickey Mouse. Here, the natural wonders of the Yucatan are the starring attraction, and every visitor an adventurer.

Xcaret is full of wonders that invite you to jump right in. Foremost among them is the famous lagoon that has long drawn sightseers and snorkelers to this stretch of coastline just south of Playa del Carmen. The lagoon, where fresh water springs melt into the aquamarine tints of the Caribbean, is rich with bright tropical fish.

Even more intriguing is an underground river. An army of workers spent three months exploring a labyrinth of cenotes, underwater caves and submerged rivers before revving up their jackhammers to open up several caverns and widen the natural channels linking them. Now, visitors don life jackets and float along the incredibly clear and natural-looking subterranean waterway. In some places along the stream, splinters of sunshine jab through rocky crevices to pierce the waters and spangle tiny fish. In others, light washes in through ventilation holes carved in living stone; the eerie illumination lends a blue cast to the waters.

Elsewhere at Xcaret are Mayan ruins. Lots of them. Nearly 2,000 structures--temples, pyramids, ceremonial platforms, defensive walls--are scattered through Xcaret’s 250 acres. Some are blanketed with vegetation; others have been excavated and rebuilt. Quintana, who is Mexican, believes the site may be the ancient city of Pole (PO-lay), a departure point for Mayan pilgrims bound for the island of Cozumel.

At Pole, travelers from all over southern Mexico, Guatemala and Belize paused to pray and make religious offerings before boarding the long canoes that would ferry them to island shrines, where they would pay homage to Ixchel, the goddess of fertility, childbirth and the moon.

Pole has a darker fame, as well. During the early stages of the Spanish conquest of Mexico, the conquistador Montejo garrisoned 20 sick and wounded soldiers at Pole; upon his return only skeletons remained. Quintana maintains the men were eaten.

Despite the allure of river, ruin and lagoon, most of the 600 or so tourists who trek to Xcaret from Cancun each day spend their time at the beach, lollygagging in the thatched-roof shade of palapas or floating in cadmium-yellow inner tubes.

It’s easy to see why. The artificial waterfront rivals anything nature has to offer. The strand is straight out of some South Sea fantasy. A scimitar of sand edges a cozy blue-green bay lined with palms. Just behind the beach rises a limestone knob crisscrossed with hiking trails and fish-filled, rock-lined canals that lure snorkelers.

To create this idyll, Xcaret laborers have transplanted thousands of full-grown palm trees and tens of thousands of smaller plants. Peacocks now strut and preen through the trees.

Leaving the maze of canals and stretching toward the rising sun, an arching, palm-lined stone walkway nearly encloses the bay. The processional also serves as a breakwater, soothing the already limpid waters of the swimming area. At the ocean end stands a thatch-roofed bar big enough to enclose a three-story house.

In the shadow of that breezy bar you’ll see a grid of fence and pier. Mexico’s first swim-with-the-dolphins program opened early this year. Four dolphins enthusiastically interact with humans several times a day. During a typical program, participants listen to an educational tape, then enter the bathtub-warm watery world of the dolphins to frolic with the sleek sea creatures. Finally, in a scene right out of the old TV series “Flipper,” a pair of dolphins proffer their fins for rides.

Quintana is a big, friendly guy you’re as likely to find closeted with a dozen consultants as collecting tickets at the gate. He says he has traveled the world searching for ideas to apply to his park. Ports of call have included botanical parks in Singapore, rock gardens in Taiwan and turtle sanctuaries in the Caymans, but Quintana says he has yet to find anything he couldn’t improve upon.

Quintana, who says Xcaret is his first project as an architect, happened on the site during a business trip, when he stopped off to swim in the cenote. He fell in love with the place, and soon had an opportunity to buy it. He did, planning to build a vacation home. But while prowling around the property he started finding things: the ruins, cenotes and underground river.

The place was too beautiful to be private, he decided. Visitors agree.