Bart Ghent's Profile

You might forget that the natural radioactive radiation is much higher in caves than somewhere else on the planet.

So it seems pretty, but it is not so healthy

See also:
http://www.nps.gov/wica/naturescience/abstract-radon-radiation-in-wind-cave.htm
http://www.ncbi.nlm.nih.gov/pubmed/8026972
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVS-4S6P260-F&_user=794998&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=956995476&_rerunOrigin=google&_acct=C000043466&_version=1&_urlVersion=0&_userid=794998&md5=129a56fed560819125a3d9c7c950eb09
http://www.onemine.org/search/summary.cfm/Alpha-Radiation-In-Natural-Caves?d=14341D6E335C7ADD9BF0B610F94AEA5907E0A7D738EF0D3CF715D07323C97F0F3784