Some of the world’s strangest lakes are filled not with water but with asphalt, also known bitumen, the same material that roads are paved with.

The great majority of asphalt that is used today is derived from petroleum, but asphalt is also found in concentrated form in nature. Sometimes they seep from the ground and create large puddles known as tar pits or asphalt lakes. At other times, they are found soaked in sands, as in Athabasca oil sands in northeastern Alberta, Canada, which is the world’s largest deposit of natural bitumen. Asphalt is also known to erupt in underwater volcanoes, but these are relatively rare and were discovered only in 2003.

La Brea Tar Pits in Los Angles. Photo credit: Betsy Weber/Flickr