Swildon's Hole

Swildon’s Hole is a cave near Priddy in Somerset. It lies beneath the Mendip Hills and stretches for more than nine kilometres, making it the longest cave on the hills. The cave system connects to Priddy Green Sink and forms part of a protected scientific site. Its name may come from Swithun, an Anglo-Saxon bishop connected to the area. The entrance is a small triangular opening in a stone blockhouse surrounded by trees. Groups often explore the cave together, and the site has been studied for over a century.

Explorers first entered the cave in 1901, reaching the 40 foot pot within a few years. Early trips continued despite a landowner’s ban, and by 1921 cavers had reached the first sump. Divers finally passed Sump 1 in 1936, and later sumps were explored soon after. Today eleven main sumps have been passed, though Sump 12 remains impassable. The water in the cave flows to Wookey Hole Caves, as shown by dye tests in the 1930s.

Inside, the cave has a varied system shaped by an active stream. Passages range from narrow crawls to large chambers with steep drops. Some parts are dry fossil tunnels, while others feature waterfalls and sumps. The cave includes vadose and phreatic sections, creating different passage shapes. A short round trip follows abandoned phreatic tubes, and some sumps can be dived without special equipment. The connection to Priddy Green Sink was made in 1996 after months of digging and blasting.