San Sebastián de las Grutas

San Sebastián de las Grutas is a village in the municipality of Villa Sola de Vega, in Oaxaca's Sierra Sur, reached by a side road that leaves Federal Highway 131, the road from Oaxaca city to Puerto Escondido, at El Vado. It had 929 inhabitants in 2020, making it the second-largest locality in the municipality. As its name says, it is known for its caves, which the community runs as an ecotourism centre at Paraje Ojo de Agua, just outside the village.

The area holds several caves, but only one dry, fossil branch has been opened to visitors. The guided route runs for about 400 to 500 m through a through-passage of five chambers between 20 and 70 m high, decorated with columns and stalagmites; the state tourism office lists one stalagmite at 15.5 m tall and another, 7.5 m tall, with a diameter of almost 8 m. Halfway through, you can hear an underground river flowing about 30 m below the walkway, and visitors with some fitness can rappel down to it with the local guides. The tour leaves the cave by a long stone staircase over the rubble of a collapsed roof, an exit more striking than the entrance. Skylights near the entrance are how the first explorers got in; local tradition says the caves were found when people climbed down a hole after an animal from a shepherd's flock fell into it.

The underground river comes back to the surface at the Ojo de Agua, a karst spring surrounded by a small forest with trails and benches, a pleasant place to rest before or after the cave. How much water flows depends strongly on the season. The cave is often described online as the largest in the Americas, but that is not true: the deep cave systems of Huautla, in northern Oaxaca, are far larger. San Sebastián is a modest, village-run cave, best visited as a day trip from Oaxaca city or as a stop on the road to the coast.