Over the years I have been in a few natural ice caves of active glaciers. They are cool but also unforgiving as friends found out:
http://publications.americanalpinecl...son-Ruth-Gorge
The caves on Mt. Hood:
http://www.opb.org/glaciercaves/
have recently collapsed:
http://www.oregonlive.com/pacific-no...ds_best_k.html