Beaver Dam Visible from Space!

I read a story today about a beaver dam, found in Canada, that is 2,800 feet long. A Canadian ecologist stumbled upon it in Alberta's Wood Buffalo National Park, and claims that it is now the largest beaver dam in the world. Some people believe that the dam was started in the 1970's, and it has been steadily built up by generations of beavers. I have now begun wondering how many other structures in the world have been created by animals working across generations. I immediately think of all coral reefs, possibly some termite mounds, and the Great Pyramid in Egypt (as well as all human cities). Does anyone else have any ideas?