The sheer stone walls of Sumidero Canyon rise hundreds of meters—and in one spot a full kilometer—above the tranquil river below, an awe-inspiring channel that’s one of Chiapas’s most recognizable and impressive natural wonders.

Two-hour boat tours of the canyon leave from Chiapa de Corzo, winding 40 kilometers downriver to the Chicoasén Dam. It’s a spectacular neck-cramping journey, and highly recommended as a day trip from either Tuxtla Gutiérrez or San Cristóbal.

Agencies in both cities offer package tours, but it’s perfectly easy to do it yourself, by car or combi, especially if you leave the afternoon to enjoy Chiapa de Corzo’s museums and architecture.

The canyon was tens, even hundreds, of meters deeper before 1981 and the construction of the Chicoasén Dam, one of three presas on the mighty Río Grijalva. In Chiapa de Corzo, a painting in the Ex-Convento de Santo Domingo portrays an infamous story associated with the canyon: Early in the conquest, an indigenous community was invaded by Spanish troops. They fought fiercely, but could not defeat their better-armed opponents.

Facing defeat, the indigenous men and women—many holding their children—leapt from the canyon walls to their deaths, rather than be captured.

Getting to Parque Nacional Cañón del Sumidero

Combis from Tuxtla Gutiérrez (US$1, 40 mins, 5 Calle Ote. Sur and 1 Av. Sur Pte.) leave every 10 minutes from 6 a.m. to 10 p.m. and drop you on the north side of Chiapa de Corzo’s central plaza. Catch return buses in the same place, on the opposite side of the street.

From San Cristóbal, take any Tuxtla-bound combi (US$3, 45 mins) from their stop on Carretera Panamericana at Avenida Insurgentes, near the ADO bus terminal. Combis from San Cristóbal don’t enter Chiapas de Corzo proper, so ask to be dropped at the first puente peatonal (foot bridge, a short distance after the toll booth); there, cross to the other side and catch a taxi (US$2.50) or colectivo into town (US$0.45). If you get dropped at the second foot bridge—some drivers seem to prefer stopping there—you can still cross and get a ride into town, it’s just a bit further.