Cave found on the moon?

[Mike]

A deep hole on the moon that could open into a vast underground tunnel has been found for the first time. The discovery strengthens evidence for subsurface, lava-carved channels that could shield future human colonists from space radiation and other hazards.

The moon seems to possess long, winding tunnels called lava tubes that are similar to structures seen on Earth. They are created when the top of a stream of molten rock solidifies and the lava inside drains away, leaving a hollow tube of rock.

Their existence on the moon is hinted at based on observations of sinuous rilles – long, winding depressions carved into the lunar surface by the flow of lava. Some sections of the rilles have collapsed, suggesting that hollow lava tubes hide beneath at least some of the rilles.

More... http://www.newscientist.com/article/dn18030-found-first-skylight-on-the-moon.html?DCMP=OTC-rss&nsref=online-news