WORLD'S BIGGEST BEAVER DAM
This massive beaver dam (huh huh, I said "beaver") is located at the southern edge of Wood Buffalo National Park in Alberta, Canada. The dam, only discovered in 2007, is in a fairly inaccessible area and was discovered on Google Earth by Researcher Jean Thie.
The dam is almost 3,000 meters long and it's suspected that construction of it must have begun in the 1970's. Since then, it has been maintained by generations of several beaver families who use it for protection against predators. The dam is so old that new trees are growing inside of it turning parts of it green.
Just to put this into perspective -- Hoover Dam is the world's largest man-made dam and it's a measly 1,244 meters across.