9 Ноябрь 2011 Last updated at 11:01 ET
Potholers have created what they believe to be the biggest cave network in Britain under Cumbria, Lancashire and Yorkshire.
Cavers have connected more the 60 miles (about 102 km) of caverns and natural tunnels beneath the high ground near Kirkby Lonsdale in Cumbria.
The caves stretch through Cumbria, Lancashire and Yorkshire, earning its name of the Three Counties System.
The project has taken more than 40 years to complete.
Deep under the Pennines, a group of cavers have cleared a way through clay and boulders to reconnect two cave systems separated at the end of the last Ice Age. . . . Read Complete Report