One of two caverns that can be visited on the Heights of Abraham. A natural cave which has been much modified by mining, the Great Masson Cavern has no stalactites or stalagmites due to a clay-like deposit which inhibits formation but the cavern does have some formations. It was first opened as a tourist attraction in the Victorian era. Today the entire original tourist route is on show with the Great Cavern, Tinker's Shaft and the rear exit being closed for a while in the late 20th century.