MOST people head straight for the Yucatan beaches when visiting Mexico, but I am bound for the southern province of Chiapas, the final stop before Guatemala.

Just one hour's flight, but light years away from Mexico City, Chiapas is cloaked in a jungle of lost Mayan cities, waterfalls and indigenous tribes.

The province's eco-tourism projects ensure your holiday is not to their detriment.

We set off by motorboat from Chiapa de Corzo on the banks of the Rio Grijalva and scud through the 1,000 metre high Sumidero Canyon, passing 12-foot crocodiles, the air swarming with black vultures.

An isolated jetty heralds our arrival at Sumidero Eco-tourism Park, a small resort of traditional buildings with thatched roofs.

The park, which opened almost two years ago, allows visitors to enjoy the fantastic scenery, learn about the culture and wildlife - without damaging the environment. This is part animal and bird sanctuary and part adventure park, with kayaking, canoeing, abseiling and swimming.

We follow a path which leads uphill past orchids, ceiba trees and butterflies to an enclosure full of toucan, spider monkeys, two female jaguars and a puma. At the top of the hill we travel by zip wire - clinging to metal wires suspended over the treetops.

Leaving Sumidero, we pick up a bus which passes through settlements centred around crudely-built, turquoise and lime-green churches.

At 2,100 metres above sea level, the old colonial town of San Cristobal de las Casas has a central plaza lined with colonial mansions. The most compelling experience is the church of San Juan in nearby Chamula, its village peopled by Tzotzil-speaking indigenous Maya Indians.

They wear extraordinarily-bright costumes and live in houses made from mud mixed with pine needles. From across the market square, San Juan looks like an ordinary white Spanish church.

But the interior is crammed with thousands of flickering candles. There are pine needles all over the floor, the walls are lined with glass cases containing saints, and a man is playing a melancholy concertina, amid choking incense.

People are singing or chanting and a figure on the floor takes a swig of a spirit known as pox or 'white water' from an oily bottle.

A Mayan woman gulps down Coca Cola and burps loudly. She removes a live chicken from the bag beside her and raises it above the candles. With eyes closed and a look of intense concentration on her face, she chants, wringing the chicken's neck. After several long moments, the chicken stops moving and she sprinkles pox over its body before placing it back inside the bag.

My guide, Pepe, explains that this is a healing session, held by Mayans if they have a problem, are ill or crops fail. The Coca Cola burp brings out evil that has caused the problem. The chicken sacrifice brings back health and good fortune.

Two days later we cover a good distance down the Pan American Highway, to the Usumacinta River at Escuda Jaguar, bordering Guatemala.

Here, we get on a lancha, a yellow-painted narrowboat with a roof of tin and reeds, and after half an hour, we pull in at a remote, muddy spot.

Paths lead through the rainforest, and in the midday heat, pockets of hot air mug you.

'Don't wander off - there are venomous snakes in the rocks here," warns Pepe. The howler monkeys are shrieking and try to urinate on us.

The path deposits us close to a pyramid-shaped building which is the start of the ruined Mayan city of Yaxchil, dating from 680AD. I enter a dark labyrinth, armed with a pen-light and realise the ceiling is covered in bats and there are spiders the size of your fist.

Out in daylight, the Pequena Acropolis and the climb up 200 steps to Edificio 33, a palace with beautiful carvings, is rewarding. Yaxchil exudes an aura of mysticism, being completely wild and only reachable by boat.

On the last day, the heat of the rainforest has left my clothes sopping, and every hour we're stopping for refreshment.

We travel to the Misol-ha Waterfall. Nothing beats shedding my clothes and plunging into the icy, lime-green pool beneath the falls.

You can rent a small lodge and spend the night there. After this week you can make it a two-centre holiday, with a week on the Yucatan beaches.