Astronauts Explore Underground in Otherworldly 'CAVES' Video

An immersive new video from the European Space Agency follows a crew exploring a cave network in Sardinia, Italy. The astronauts were taking part in the Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills (CAVES) astronaut training program in July 2016. "The team explored further than any other CAVES course, mapping their progress and taking samples of the environment and life they found," ESA officials said in a statement.