On a busy Summer weekend, families enjoy the old Tarr Steps Clapper Bridge over the River Barle in Exmoor National Park, Devon, England. Crossing on the huge stone prehistoric slabs which weigh up to 5 tons apiece, children play with fishing nets, walk dogs and sit enjoying the view below of others who mess about in a small inflatable dinghy on the flowing stream. Located in a National Nature Reserve about 2.5 miles (4 km) south east of Withypool and 4 miles (6 km) north west of Dulverton, this spot is a favourite tourist place in South-West England. This typical clapper bridge construction may date to around 1000 BC. It is 180 feet (55 m) long and has 17 spans and designated by English Heritage as a grade I listed building.