Although this is closer to Tuxtla Gutierrez, Cañon de Sumidero is easily experienced as a day trip from San Cristobal. This canyon is the result of a geological fault formed millions of years ago and the slow carving of the Grijalva River. As you coast along the river in a jungle boat through the gorge, you have magnificent views of the canyon with its 2,500-foot-high walls, which were even higher before the Chicoasen dam, the fifth highest in the world, was built in 1981. You see impressive geological formations, such as the Christmas Tree Falls, the Cave of Silence, and the Cave of Colors. Your approximately three-hour trip ends where the narrow canyon opens up into a sunny valley with magical waterfalls surrounded by wide, green glens.
The spectacular, 1-kilometer-deep Sumidero Canyon was the stage for an epic battle between the Spanish and the Chiapanecan Indians, who chose to jump into the sacred canyon rather than submit to the invaders.

Spectacular scenery, from the crocodiles to the ride under a pine-shaped waterfall, including the cave of worship (still in use) in the canyon walls above the river. In one word, breathtaking.

It’s awesome place with marvellous view! Going down the river you can see a huge canyon, big birds flying high in the sky and some crocodiles resting in sunshine.

nice place .... but there is some places better in San cristobal

nice crocs and iguanas :-)