As you pass the pond on top of the mountain, you’ll see a beaver’s nest on the far side.
The Adirondack Museum in Blue Mountain Lake has a number of great exhibits. When I was there recently, I took a shot of this three-dimensional display which shows what the inside of a beaver’s nest looks like (Click on this picture to see it in full screen.).
The entrance is actually underwater and the beavers swim into it from below. The mud and sticks form a protective cover which hardens almost like cement. So now you know what the inside of a beaver’s house looks like.