Mendon Ponds contains a number of unique glacially created land structures, including a kettle hole known as the "Devil's Bathtub", eskers, a floating sphagnum moss peat bog, and kames.
At the northernwestern end of the line of other glacial ponds and lakes near the "Devil's Bathtub", [REF] there is a sphagnum moss peat bog, where the build-up of moss has created a floating island in the middle of the lake.