There is a large ice cave or glacier cave out at the Mendenhall Glacier in Juneau Alaska. Had to go explore it a couple of times this last week and a half. The large end of the tunnel is about 30 feet high and the narrow end is about 8 feet high and the length of the tunnel is about 100 feet long. My son went with me to explore and can be seen in a couple of the shots. Our first trip out there were a couple of ice climbers having fun on the berg. This cave is located on a very large ice berg that broke away from the face of the glacier and then froze in place for the winter right in front of the glacier. The flat floor of the tunnel is the lake water that has froze for the winter and appears to be about 4 feet thick.