Tar Tunnel

Tar Tunnel is an abandoned brick-lined tunnel on the north bank of the River Severn at Coalport, in the Ironbridge Gorge, Shropshire, England. It was dug to carry coal, but it became famous for something else entirely: natural bitumen that still seeps from its walls.

What is the Tar Tunnel?

The tunnel runs into the valley side near the former porcelain works and canal at Coalport. It lies within the Ironbridge Gorge, a UNESCO World Heritage Site since 1986, and is now managed by the National Trust. Its coordinates are roughly 52.62 N, 2.45 W.

How was it built?

Work began in October 1786 under the ironmaster William Reynolds. The idea was practical: drive a tunnel into the hillside to reach coal workings and let boats carry the coal underground straight to the river. Some accounts date the strike to 1787, so sources differ by a year.

Instead of coal, the diggers cut through a layer of natural bitumen. About 300 metres from the entrance, a spring of thick black tar began to flow. Reynolds had samples analysed, and they were identified as natural bitumen. Rather than abandon the project, the owners started harvesting it.

What was the tar used for?

The bitumen was channelled out, processed and sold. Its main early uses were waterproofing ropes and sealing wooden ships. Small amounts were bottled as "Betton's British Oil" and sold as a remedy. Output declined steadily: by the 1820s it was down to about 10 barrels a year, and by the 1840s the flow had dried up commercially. Coal was still moved through the tunnel in 1801.

Rediscovery

The tunnel was forgotten for a long time, then rediscovered, stabilised and partly opened to visitors in the 1960s. Bitumen still seeps from the walls today, which makes it a rare survivor among Britain's industrial heritage sites.

Frequently asked questions

Where is the Tar Tunnel? At Coalport in the Ironbridge Gorge, on the north bank of the Severn, close to Telford.

Can I go inside? Access has changed over time. Art Fund listed a reopening date of 1 December 2026, while the Ironbridge Gorge Museum Trust page described it as closed. Check the official website for current opening details before you go.

Who runs it? The National Trust, which acquired ten museums from the Ironbridge Gorge Museum Trust in 2026, the Tar Tunnel among them.

Is the tar still flowing? Commercial production ended in the 19th century, but natural bitumen still appears on the tunnel walls.

Who is it for?

Anyone interested in industrial history, geology or unusual heritage sites. Pair a visit with the rest of Coalport and other Ironbridge Gorge sights such as the famous iron bridge over the Severn. The Tar Tunnel shows how an unexpected find turned a failed canal scheme into a short-lived but profitable business, and left behind one of the Industrial Revolution's strangest places.