I'm looking for some suggestions on materials for making a cave. It's going to be outside on the midway of a theme park. Right now, I'm thinking it's going to be approximately 10ft wide, 8ft tall, and 15ft long. I need some kind of spray-on latex or fake-concrete material and something for it to attach to. I'm thinking the formations of the rocks will be sculpted out of chicken wire.
Any suggestions I'm all ears!