Glacial Pot Holes: Shelburne Falls, MA.

When the last of the glaciers melted, the CT River valley was flooded, creating lake Hitchcock. As the lake drained, sand and stone began to erode the metamorphic rock, some of the deposits getting stuck in cracks along the riverbed and inevitably eroding holes into the earth.

The town has since closed it off, but this has been a large summer attraction for the local populous. Several tiers of the falls have holes you can swim into and come out in other areas. Best place I've ever swam!