Cave Algar do Karvanen - an ancient lava tube, or the so-called volcanic crater on the island of Terceira. The cave is located in the central part of the island in the district of Porto Jude in the municipality of Angra do Heroísmo.

The word "Algar" translated from Portuguese means a natural depression in the land, which, unlike most of the caves, located vertically, like a well. The word in Portuguese comes from the Arabic language, its original meaning was "borders". "Karvan" with the Portuguese means "coal", but in the cave coal there, it's just focus on that dark cave.

Terceira Island is formed by four volcanoes - Pico Alto, Santa Barbara, Zhilerme Moniz and Cinco Pikush along the basaltic fissure zone that divides the island in half and stretches from the northwest to the southeast. Cave Algar do Karvanen directly adjacent to the caldera Zhilerme Moniz, and is located at an altitude of 550 meters above sea level. There is a possibility to go down for about 100 meters, where there is a lake with crystal clear water.

The cave is known for its unique mineralogical characteristics of stalactites and stalagmites. They are considered the most beautiful in the Azores archipelago. Caves area - 40.5 hectares. Due to its geological characteristics of this cave is recognized as "regional natural monument".

The existence of the cave has been known for a long time, but due to the fact that the inside is very dark, and it was dangerous to go down, the cave has been insufficiently explored. In January 1893, in the cave after the first expedition. The second study was carried out of the cave in the twentieth century, in 1934. After this expedition was to draw a map of the cave.