A set of seven 'planetary parks' have been proposed for the conservation of the martian environment by two European scientists. Each of the parks contain representative features of the landscape on Mars.
The Polar Park would protect the martian ice cap; Olympus Park would make the largest volcano in the solar system, Olympus Mons, safe from commercialism and exploitation. Charles Cockell, a Britich microbiologist, and Gerda Horneck, a German astrobiologist, point out that many parks on Earth were established to protect their natural beauty, not just wildlife.
Among the many barriers to this proposal is the fact that while many nations, including the United States, Russia and China, have signed the UN Outer Space Treaty, few have ratified the 1979 Moon Agreement. This agreement specifically seeks to regulate the exploration and exploitation of natural resources found on the Moon and other celestial bodies; the U.S. has not ratified this agreement.
Also, natural and manmade caves on the Moon were used for recreation in Robert Heinlein's The Menace From Earth; loonies used Bat's Wings to flap around and enjoy themselves.
(This Science Fiction in the News story used with permission from Technovelgy.com - where science meets fiction.)