San Juan Chamula

San Juan Chamula is the main town of the indigenous Chamula people who live in the area. The town feels a world apart from much of the rest of Mexico. Most Chamulas wear traditional garments. Women wear heavy black skirts that are made from naturally tinned wool, men wear white vests also from wool. The economic status can be seen from the garments; heavy thick skirts and pure white vests indicate wealth whereas thin skirts and spotty vests are worn by the poor. Though some Chamulas have attained some level of prosperity, the vast majority is very poor.
The Chamula people have a very distinct culture. Most visibly, their religion, though considered Catholicism, is a blend of Christianity and Mayan traditions. Their main place of worship is the church of San Juan Chamula. If you get to know Chamulas a little more you might also witness some baffling features in their everyday life and value system: they have taken law into their own hands and sometimes use force to bring people to justice. At the same time you may find families who see children foremost as an economic burden or people who are willing to sell their children like some commodity not showing any emotional connection towards their children as they are making an offer to do so.

There are collectivos all day from San Cristóbal de las Casas.
Although you do not need to go with a tour it takes about twenty minutes in a collectivo -- taking a guided tour does help give you context for what you see in the villages, and with a good guide you really get a feel for daily Maya life that you could never gain alone.
Most of the agencies in San Cristóbal offer half-day tours to Chamula and Zinacantán that leave at 09:30.

It is easy to walk anywhere in San Juan de Chamula.

The church in San Juan Chamula is a must see. Inside you can see a seemingly random blend of Mayan traditions with Catholicism. The main altar shows San Juan (John the Baptist) instead of Jesus, and saints which resemble gods are lined up along the walls church.
People go to church to be healed rather than to pray for salvation. They perform rituals on the church floor (covered by pine needles instead of benches) in the community of the family which usually involve a lot of candles and sometimes Pox (liquor) that is also served to small children.
You must not take any photos in the church -- this is highly offensive to the people and could result in you losing your camera.

There is a big market in front of the church -- you can buy locally made handicrafts of wool.
They make purses, skirts, dolls, etc.
The town itself is extremely poor and it would be helpful if you supported the community and purchased some of their handmade goods.

There are no popular lodging options in San Juan Chamula. Virtually all visitors come on a day trip from San Cristóbal.

Rule of Law is not really upheld in San Juan Chamula and most of the Chamula area. Although there have been no major incidents involving tourists, take into account that issues are often resolved by force. (One could argue that this anarchic system has been established in response to the centuries of negligence and despise by the government and society; quite contrary to the response of the Zapatista movement though.) This is to some extent facilitated by the fact that San Juan Chamula has its own police force and that regular police or military are not allowed inside the village.
In the past there have been numerous incidents (e.g., in late 2015, people who went to collect a payment for a car were burned alive; also in late 2015, the entire hospital was taken for ransom when a child died after extreme negligence from its family; in mid 2016 a group of people including the mayor was fatally shot on the town square, ...) Since crimes usually go unpunished, the area is also notorious for car theft and said to house drug labs.
However, the community appears to have a huge interest in you coming to their town and markets which has apparently kept tourists safe from any harm.