Tar Tunnel

Walk into an 18th-century tunnel in Bridgnorth and you'll smell it before you see it - a thick, bituminous tang that hasn't changed in 250 years. The Tar Tunnel is exactly what it sounds: a narrow passageway carved through coal measures where natural bitumen seeps from the rock face, pooling on the floor in glossy black puddles. It's genuinely odd.

You're essentially standing inside an industrial curiosity from the Industrial Revolution. Local miners discovered the tar oozing out of the ground and realized they could collect it, bottle it, and sell it as a commercial product. For a brief spell, this became a working enterprise - visitors were charged to walk through and witness the stuff leaking from the walls. Now the Ironbridge Gorge Museum Trust runs it, and you can shuffle through the same 300-metre passage, ducking under a low ceiling, watching for the glossy seams.

It's not a long visit - twenty minutes tops - but it's the sort of place that sticks with you. Kids find it properly fascinating; adults get a genuine sense of how Victorians extracted value from absolutely everything. History types will appreciate the geology-meets-commerce angle. The air inside is cool and damp, and the smell is unmistakable.

If you're basing yourself at one of the nearby camping spots - Irongorge, Hay & Hedgerow, or Worfe - the Tar Tunnel works brilliantly as a half-hour detour between longer walks around the Ironbridge Gorge. It's free to enter and costs nothing but a bit of your time, though check opening hours before you visit.