Gliding along the Llangollen Canal across the River Dee valley in North Wales in a flat bottom narrow boat at a top speed of 4 miles/hour is one of the most relaxing and memorable holidays. The aqueduct is one of the most awesome engineering feats on the canal network and a narrowboat, (a specialized craft for operation on the narrow canals of England, Scotland and Wales) is the best way to navigate it. A 11-mile (18 km) section of the canal from Gledrid Bridge near Rhoswiel through to the Horseshoe Falls, which includes Chirk Aqueduct and Pontcysyllte Aqueduct, was declared a World Heritage Site by UNESCO. Wales.