This small cave by the lake was used by the Duke of Portland in the 19th century to moor his boat.

When Leslie Armstrong made his initial exploration at the cave, he unfortunately used explosives to remove the hard concrete floor which sealed the softer cave-earth deposits. Although he records bone fragments from this work nothing survives today. The location of this cave with water running into it from the lake, led both Armstrong and subsequent archaeologists to abandon their work due to flooding.