Pontcysyllte Aqueduct and Canal

Narrowboats cross the sky in north-eastern Wales, gliding along Thomas Telford's Pontcysyllte Aqueduct — a cast- and wrought-iron trough carried on slender arches high above the River Dee. Completed in the early 19th century, the 18-kilometre canal conquers difficult country without a single lock, engineering audacity that influenced projects worldwide. UNESCO inscribed the aqueduct and canal in 2009.