From the World Heritage inscription:
The Pontcysyllte Canal is a remarkable example of the construction of a human-engineered waterway in a difficult geographical environment, at the end of the 18th century and the start of the 19th century. It required extensive and boldly conceived civil engineering works. The Pontcysyllte Aqueduct is a pioneering masterpiece of engineering and monumental architecture by the famous civil engineer Thomas Telford. It was constructed using metal arches supported by tall, slender masonry piers. The Pontcysyllte Aqueduct and Canal are early and outstanding examples of the innovations brought about by the Industrial Revolution in Britain, where they made decisive development in transport capacities possible. They bear witness to very substantial international interchanges and influences in the fields of inland waterways, civil engineering, land-use planning, and the application of iron in structural design.
Of the many world heritage sites I’ve visited, I’ve had the biggest surprises visiting the industrial themed sites. They don’t get the same amount of attention as the ancient sites do, but they are just as important to the development of the modern world.
The Pontcysyllte Aqueduct doesn’t look like much at first, but at the time it was constructed in 1805, it was truly a wonder of the world. The aqueduct carries water traffic 126 ft (38.4m) above the valley which it crosses. It is considered perhaps the greatest engineering achievement of the great 19th Century engineer, Thomas Telford.
The aqueduct can be cross on foot or by canal barge. During the summer, there are many barges which carry passengers across the aqueduct.
View my complete list of UNESCO World Heritage Sites.