Tween Twins Hole, also known as Fester Hole, is a cave in Burrington Combe, Mendip, UK.
It was discovered by members of the Wessex Cave Club in 2016 after many years digging at the site. The cave is designated a SSSI (Site of Special Scientific Interest) and was gated soon after its discovery with the permission and encouragement of the landowner and English Nature to preserve it for future generations.
A leader system is now in place and trips to the cave can be organised via this website. Available dates for visits to the cave are published at the start of each year and allocated on a first come-first served basis. Available dates can be viewed on the Bookings Calender. If you would like to take up an available trip please complete the Booking Request form to reserve you trip. The cave operates a closed season from 31st October to 1 April each year to protect hibernating bats and to avoid bringing mud from the original dug entrance into the cave.
A list of the guidelines for visiting cavers can be found here.