Gruta das Torres Vedras is a cave with lava tubes, a geological formation of volcanic origin. Lava tubes are formed as a result of uneven cooling of streams of molten volcanic magma in contact with air.

The cave is located outside the area of criação Velha, municipality of Madalena, in the Western part of the island of Pico, is a group of interconnected lava tubes, the width of which ranges from 0, 5 m to 22 m, height - 1, 2 m to 15 m. the cave Is situated at an altitude of 300 meters. Its length is approximately 5, 2 km, and Gruta das Torres Vedras is the longest lava cave in the Azores.

The exact date of the opening of the cave is not known, but the first scientific expedition was sent there in 1990. The uniqueness of the cave is its impressive dimensions of the drainage network, which is seen in more than seven layers on the walls of the cave with side ledges and three eaves.

Gruta das Torres Vedras is one of 17 caves on the island of Pico, which is a UNESCO world heritage site as part of the phenomenon of volcanic origin in the mountains of the Azores. In addition, Gruta das Torres Vedras is one of 28 caves that open on the island of Pico, which size is considered large enough. Cave ranks eighth in size of the crater among the other caves on this island, which, it should be noted, has more caves than any other island on the Azores archipelago.

Open to visitors Gruta das Torres Vedras was in 2005. Here is organized tourist excursions. The first 450 meters, the group is escorted by a guide. In the group recruited 15 people, and each visitor is supplied with protective gear, which includes helmet, equipped with light bulbs that help to see in the dark. At the entrance to the cave has built a visitors centre where there is an auditorium where you can watch a movie about this natural phenomenon.