Postbridge, Dartmoor, SW England, attracts tourists from all over the world.
This is perhaps the most well-known intact 2-span medieval Clapper Bridges of its kind.
It was built to transport the pack-horse trains carrying locally-mined tin across the
East River Dart. The newer bridge behind was built in 1780.
There are better photos of Postbridge than this but this is the only one I have which
lends it a sense of true scale thanks to the secondary subject provided by the little boy
paddling in the river to the left of shot.
(View it at full size and move the slider along to get the best impression.)
If you go to Bellever bridge (nearby) you will find a similar situation with
two bridges, except that the clapper bridge there has missing spans.
There is however another interesting clapper bridge on the river Teign at Batworthy,
near the Scorhill stone circle.

Much more detailed information here:

www.legendarydartmoor.co.uk/post_bridge.htm

and also the official Dartmoor NPA site

www.dartmoor-npa.gov.uk/index/visiting/vi-planningyourvisit/vi-infocentres/vi-postbridgeinfocentre.htm