It is a unique place of worship, where Tzotzil Indian peasants pray to a mixture of Jesus, God, the Sun and ancient spirits. It is also the cradle of a tragically demeaning con by local wealthy landowners and political leaders who have the gullible peasants at their mercy. The scam gives the caciques (bosses) ever more land and ever more of the poor Indians' hard-earned cash.
The bosses and political leaders went into hiding last week as it emerged that many of the area's 50,000 people had disappeared, apparently to join the Zapatista uprising. Thousands of others had earlier been 'expelled' for turning to evangelical faiths, more specifically for refusing to drink, smoke or 'co- operate in our fiestas'.
The expulsados (expelled ones) now live in shanty towns outside the town of San Cristobal de las Casas, some five miles from here. There they clap and sing in their own churches, mostly pentecostal, in services reminiscent of black gospel meetings in the southern United States.
In the big San Juan Bautista church, there are no pews, but plenty of alcohol and soft drinks, along with tens of thousands of flickering candles of all colours, shapes and sizes. These are laid out in rows on cleared patches of the floor. Each patch is a shrine, where a group of Tzotzil Indians prays after laying out glassfuls or bottles of posh (rough sugarcane alcohol), cola or other soft drinks as offerings to their part-Catholic, part-Indian conception of God.
Just inside the entrance two villagers sat on a bench engaged in slurred conversation, clearly having drunk at least as much posh as they had offered. Capping it all was the taped background music, as though from bagpipes, continuously repeating such melodies as 'O Come All Ye Faithful' and 'Rudolph the Red-nosed Reindeer'. A light machine flashed multi-coloured bulbs in rhythm.
Outside the church an Indian family of five also held 'holy' drinks bottles as they stood facing south, praying out loud as they gazed into a cloudless blue sky.
The husband, Manuel Perez Hernandez, 50, later explained: 'We pray to Tatik, our God.' We asked him what that meant in terms of Catholicism. To the Tzotzils of Chamula, 'tatik' means the Sun, but also encapsulates God the Father as well as Jesus and the Virgin Mary. 'Jesus is our Lord. Tatik is Jesus, God and the Sun,' Mr Perez said, suggesting we might invite him to a glass of posh for further explanation.
The key to the use of alcohol, soft drinks and so many candles, all of them sold next to the church at prices the peasants cannot but somehow do afford, is simple. For years, a group of local caciques have cashed in on the peasants' combination of faith and gullibility. The caciques just happen to hold the concessions to the posh, the soft drinks, the candles, the local taxi service and anything else that brings in money.
'The traditional doctors use Coca-Cola to cure many ailments,' Lucio Munoz, 27, the local 'tourism representative', himself a Tzotzil, assured us in all sincerity. 'They rub it on to cure skin ailments but it has helped many recover from serious illness.'
With the collusion of the village mayor, inevitably from the ruling Institutional Revolutionary Party (PRI) of President Carlos Salinas de Gortari, the peasants are subdued, robbed, turned into drunkards and, through built-up debt, gradually stripped of their land. A small bottle of posh costs 3 new pesos (3,000 old pesos), or around dollars 1 (65p), a stubby candle in a glass at least 20 new pesos, almost dollars 7. Worshippers in the church lit eight rows of candles.
Each shrine cost a family several hundred new pesos, more than dollars 100, or an entire month's income. The only way they can pay is to use their possessions, then their homes, then plots of their land as collateral. Under the present system, the caciques cannot lose. Villages such as San Juan Chamula are a law unto themselves. The caciques choose the PRI candidate who will be mayor and the peasants are ordered to vote for him.
In villages or towns in doubt, where some form of voting privacy is observed out of necessity, ballot- stuffing has traditionally ensured 'the right result' for the party that has ruled for more than 60 years.
The Zapatista uprising, behind a call for land reform and an end to electoral fraud, has the bosses and the so-called priistas (the ruling party people) worried.
'Some people here support the government, some don't,' Mr Munoz told us as we handed over our 2 new pesos each to enter the church. 'Some people went to join the Zapatistas,' he said, adding that some of the Zapatista National Liberation Army (EZLN) had passed outside the village's gates after fleeing San Cristobal last week.
He told us several hundred EZLN members remained, in three separate groups, in the small town of San Andres, a few miles further uphill from here. The Mexican army has dug in a few hundred yards from Chamula, blocking the highway into San Cristobal. But Mr Munoz said he believed many guerrillas had fled into caves in sheer cliffs that tower above thick forests in a remote area between San Andres and the town of Bochil.