Learning about Caves and Caverns

If you are going to make some cavernous setting locations available for exploration, it doesn't hurt to do a little research about how they are formed, what naturally occurs in them in regard to obstacles and dangers, and, of course, plant and animal life. There are a lot of free resouces online, of course, and few more reputable than NOVA.  Check out some of their slideshows and videos for inspirarion.