Reigate Fort

You're looking at what amounts to a grown-up history puzzle on Reigate Hill, just outside Tadworth. This is the remains of a Victorian fort - properly substantial earthworks and brick structures that once formed part of London's outer defence ring. Walk around the site and you can still make out the original gun emplacements, the ditch systems, and those distinctive casemates where soldiers would have sheltered. It's managed by the National Trust, so the grounds are accessible and reasonably well-kept.

The fort itself pulls in two types of visitors: military history enthusiasts who'll spend a good hour tracing the fortifications and working out the tactical layout, and casual walkers who treat it as a pleasant loop on the way around Reigate Hill. Fair warning - it's not a museum with interpretation boards or guides. You need to bring some curiosity and maybe do a bit of research beforehand to get the most from it. Kids aged ten upwards might enjoy the scrambling-about-on-earthworks appeal, but younger ones will probably wonder why there's no playground.

The location works brilliantly if you're staying at one of the caravan parks nearby - Alderstead Heath or Surrey Hills Park are close enough for an easy morning visit. Combine it with a walk through Gatton Park, which sits adjacent, and you've got a half-day sorted without spending a fortune. Admission is free, though details on exact opening times can be patchy, so check the National Trust website before you set out.