The Cave of Swallows is in which Mexican state?

The Cave of Swallows is in San Luis Potosí, Mexico.

Known in Spanish as Sótano de las Golondrinas, the cave is an enormous open-air pit in the municipality of Aquismón, in the Huasteca region. Its name comes from the birds that gather around the shaft, although the most commonly seen species include white-collared swifts and parrots rather than true swallows.

The cave’s elliptical opening measures roughly 135 metres by 305 metres, while the shaft drops more than 300 metres from its higher rim. It formed in Cretaceous limestone through the enlargement of a vertical fracture. The site was known locally for centuries; its first documented exploration took place in December 1966, followed by the first recorded descent in April 1967.

A common mix-up is confusing the cave with a similarly dramatic Mexican cavern in another state. San Luis Potosí is the state, while Aquismón is the municipality. Visitors can view the opening relatively easily, but descending requires technical equipment, permits and serious climbing or caving experience.