Pontcysyllte Aqueduct   The full name of Pontcysyllte Aqueduct carries the Llangollen Canal over the River Dee. In Welsh its called Traphont Ddwr Pontcysyllte, taking 10 years to design and build and completed in 1805, it is the oldest and longest navigable aqueduct in Great Britain and the highest in the world, measuring 126 feet high and 307 metres long. The structure is a grade 1 listed building and one of the few attractions in the U.K. to be granted World Heritage Status. We think the best way to experience this is with a boat with Crest Narrowboats.