Caverna Aroe Jari

Aroe Jari (MT-0038), meaning Soul Shelter in Bororo language, also called Frenchman Cave, is the largest sandstone cavern in Brazil, located 46 km from the town of Chapada dos Guimarães, inside the area of Fazenda Agua Fria, north of the state of Mato Grosso. It is 1550 meters long, extremely flat and has numerous waterfalls. Near the entrance, there is a stream which formed the Blue Lagoon, a natural swimming pool with crystal blue water that is reflected on the walls of the cave.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).