Pontcysyllte Aqueduct

The Pontcysyllte Aqueduct carries the Llangollen Canal 307 metres across the River Dee valley at a height of 39 metres — making it both the longest and the highest canal aqueduct in Britain. Completed in 1805 after ten years of construction under Thomas Telford and William Jessop, it was a pioneering achievement in cast-iron engineering and became a UNESCO World Heritage Site in 2009.

The experience of crossing it is memorable. You can walk across on the towpath, which is wide enough for two people abreast; canal boats cross in the trough beside you, with no barrier on the downstream side. The walk from the Pontcysyllte basin, about 11 km southeast of Wrexham via the A539, takes you through the Vale of Llangollen before you arrive at the aqueduct itself. Alternatively, boat trips depart from nearby Trevor Basin, making the crossing in a traditional narrowboat with a commentary on the engineering. The return trip on foot along the towpath takes about 45 minutes.

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A story
Thomas Telford solved the problem of carrying the Llangollen Canal across the 39-metre-deep Dee Valley by casting a cast-iron trough — just wide enough for a narrowboat — and suspending it on 19 hollow masonry piers. On one side of the trough is a towpath where horses walked; on the other side, there is no railing at all, just the trough wall and a 39-metre drop. Telford wrote that the absence of a railing was deliberate: the open side encouraged the horses not to look down. The aqueduct has been in continuous use since 1805.

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