This is an underground temple, extending 10 metres under the earth, with 13 separate rooms. It was hand carved out of the limestone with only flint, obsidian, animal bones and stone tools over 5000 years ago. There is an oracle hole, which has amazing acoustics, and, nearby, a carved circular wall, which resembles an above-ground temple. It has to be seen to be believed! It's necessary to book in advance as the number of visitors is limited and it's very popular, being unique in the world. A beautiful figurine was found here, known as the Sleeping Lady. She is on display, with other artefacts from the temples, at the National Museum of Archaeology in Valletta.