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When we think of astronauts exploring other worlds, we often forget about the weird places they also visit on Earth. 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 course's purpose is to teach skills such as leadership, teamwork and decision-making to improve their abilities in space.

"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. "They tested new techniques for making accurate 3D models of objects and the environment using standard cameras — a technique that could be used in exploring other planets." [In Pictures: Astronauts Prepare for Space by Cave Diving]

In the video, called "Another Space," orange-jumpsuited crewmembers crawl through narrow cave tunnels, pulling along gear as they go. Once they reach empty space, they carefully secure their ropes and descend into the cavern, revealing a world of beautiful rock features on the ceilings and the floors.

But there isn't much time to look around and illuminate things with lanterns. In the video, which is not narrated, the astronauts set to work collecting samples. They pick at what appears to be mold on the walls and study small, living creatures in petri dishes.

Moments of fun are allowed; at one point, the astronauts leap over a rock feature and plunge into the water, swimming and splashing. Then they wrap up their work at a base camp, reviewing the results by laptop and recording videos to share with others when they emerge.

Accompanied by skilled trainers, the crew was ESA's Pedro Duque; NASA's Jessica Meir and Richard Arnold; Japan's Aki Hoshide; China's Ye Guangfu; and Russia's Sergei Korsakov.

Follow Elizabeth Howell @howellspace, or @Spacedotcom. We're also on Facebook and Google+. Original article on