Grotta Gigante

This is one of the largest underground caves in the world. There was an underground river that a second above ground river flowed into it, forming a underground waterfall that carved out the large cave 2 million years ago.
Inside the cave are two very long wires connected to some instruments that allow geologist to make very accurate measurement of the cave. The setup can measure the change in the cave size from the moon's orbit around the Earth and the movement of the African tectonic plate.Read more