Welcome to the Beavers' Lodge, home of the Castor Canadensis, better known as the North American Beaver.  

A beaver builds his lodge with sticks and mud. Inside he creates two levels: one underwater and one level above.  His lodge is like a two-story house with his front door underwater on the bottom level to keep the predators from entering. The second story is above the water level and provides a place to keep his family warm and dry.