Furna de Água

Furna de Água is a cave system located in the municipality of Angra do Heroísmo, on the island of Terceira in the Portuguese archipelago of the Azores. The 560 metres (1, 840 ft) long volcanic lava tube, is one of the main sources of fresh water on the island, due to the presence of several springs within the cave. Although known since 1838 (and perhaps earlier), Furna de Água only began to be prospected and used in the mid-20th century.

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