 Countries are racing to establish a permanent human presence on the Moon, but astronauts will need protection from radiation and extreme temperatures. This Moon cave, the first ever found, could be the perfect shelter. It is at least 100 metres deep, with a skylight in the lunar surface and overhanging walls. Scientists have long thought that the Moon had an underground world. Professor Leonardo Correa at the University of Trento in Italy helped identify this cavern using radar.