Monmouth (A40 Gibraltar Hill) Tunnels

The tunnels beneath Gibraltar Hill in Monmouth are a proper curiosity - a network of passages carved into the rock that once served as air raid shelters during the Second World War. Walk through the narrow corridors and you're essentially moving through living history, concrete and metal fixtures still in place where civilians huddled during bombing raids. The museum setup explains the context well enough, though honestly, the tunnels themselves are the draw rather than any fancy displays.

It's not a massive undertaking - you can work through it in under an hour, which makes it ideal if you're passing through Coleford or basing yourself at one of the nearby campsites like Bracelands or Greenacres. The walk up Gibraltar Hill is a bit of a climb, but nothing that'll trouble most people. Kids find the underground passages genuinely interesting rather than educational-museum-boring, which counts for something. History enthusiasts will appreciate the wartime detail, though if you're expecting anything as dramatic as some of the larger shelter systems elsewhere in the country, manage your expectations.

The real appeal is the sense of stepping into an actual wartime moment - you can picture the fear and the makeshift comfort all at once. Pair it with a walk through the Forest of Dean nearby and you've got a solid half-day sorted. Check locally for current opening hours and admission charges before you head out, as details can be thin on the ground.