Up in the highest mountain ranges of Portugal resides a mysterious giant hole at Covão dos Conchos, Serra da Estrela, that looks like it opens up into the very core of the Earth.
Although we would love to let our imagination dream up what could possibly be lurking down inside that hole, Covão dos Conchos is actually just a dam that is part of Portugal’s hydroelectric system.
The hole is a tunnel which collects the waters of Ribeira das Naves and forwards them to the Lagoa Comprida. The tunnel is made of concrete and granite. It has 48 meters (157 ft) crown and 1,519 meters (4,983 ft) in length and is able to reach 120 thousand cubic meters.