Red Door Tunnel

The Red Door Tunnel is a short, easy walk through Portland's quarried caves - nothing fancy, but it does what it says on the tin. You'll find the entrance marked by a rather cheerful red door (naturally) carved into the stone, and it's one of several cave systems dotted around this former quarrying area. The tunnel itself is brief - maybe ten minutes if you're dawdling - but the real appeal is the industrial history on display. You're walking through passages that men spent years hacking out of the ground, and there's something quite striking about that when you're standing in it.

It's not a major expedition. The passage is low in places, so taller visitors might need to duck, and you'll want a torch because it gets properly dark. Families with young kids tend to find it entertaining rather than thrilling - the novelty wears off quickly unless your lot are proper cave enthusiasts. Walkers tackling Portland's clifftop paths often detour here as a curiosity rather than a destination.

Free admission as far as anyone can tell, though information is sparse online. Allow thirty minutes to an hour if you're combining it with a look around the other quarry caves nearby. Best visited on a clear day when the entrance isn't waterlogged. It works well as part of a broader Weymouth area holiday - Waterside and Chesil Beach Holiday Park are both within easy reach, and it takes the sting out of a rainy afternoon. Worth ten minutes of your time, though don't rearrange your itinerary around it.