While Joe was on assignment for one of his architecture clients the developer on the job showed us an interesting destination we would of never found otherwise. Out in Altoona there is a Cave preserved under the National Speleological Society called Tytoona Cave that is quite the sight to see! Kids always play down around there and some actually venture to the inside; explorer beware! We took the stroll down to the entrance of the cave which is 40 feet wide and 12 feet high consistent of limestone. This cave dates back to the 1750’s!
Plenty of resources that dive deeper into the topic. Also more photos and video.