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Man and dog, high above

A lone dog-walker, high up on Pontcysyllte Aqueduct, Llangollen.

 

The Pontcysyllte Aqueduct is a monumental and highly innovative navigable aqueduct that carries the Llangollen Canal over the River Dee valley in north-east Wales. Completed in 1805, it is a Grade I listed building and a UNESCO World Heritage Site, recognized as a masterpiece of industrial civil engineering.

 

Key Facts

Location: Trevor, near Wrexham, in North East Wales.

Designers: Chiefly Thomas Telford, with William Jessop as the more experienced supervising canal engineer.

Dimensions: It is the longest and highest aqueduct in the UK:

Length: 1,007 feet (307 meters).

Height: 126 feet (38 meters) above the River Dee.

Width/Depth: The cast-iron trough is 12 feet (3.7 meters) wide and 5.5 feet (1.7 meters) deep.

Structure: The aqueduct consists of 18 hollow stone piers supporting a trough made of cast-iron plates, a pioneering use of iron in structural design.

Construction: The project took ten years to design and build (1795-1805). A notable detail is that the lime mortar used in the masonry contained ox blood, believed to add strength.

 

Significance

The Pontcysyllte Aqueduct was a groundbreaking achievement during the Industrial Revolution, enabling efficient transport of goods like coal, slate, and iron between North East Wales and the English canal network. Its innovative use of cast iron in a bold, high structure set a new standard for transport infrastructure worldwide.

Today, the aqueduct, known as the "stream in the sky", is a major tourist attraction where visitors can walk along the towpath or take a narrow boat trip across, enjoying magnificent views of the Dee Valley.

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Uploaded on November 3, 2025
Taken on October 31, 2025