Fort Nelson

You're driving through the Hampshire countryside south of Southampton when Fort Nelson appears - a proper Victorian artillery fort, all brick and imposing angles, sitting on Portsdown Hill like it's still defending the coast from a French invasion that never came. Built in the 1860s as part of a ring of defences around Portsmouth, it's now home to the Royal Armouries' artillery collection, and it's genuinely absorbing if you're into military history or industrial design.

The fort itself is the thing - you can wander the gun emplacements, peer into the magazines, and actually understand how Victorian military engineers thought. There's a working forge where blacksmiths demonstrate period techniques, and enough brass and iron sitting around to keep anyone who likes that sort of thing occupied for a couple of hours. Kids get a kick out of it too, though a six-year-old might flag after an hour or so.

Admission is free, which is remarkable for something this substantial. You'll want to allow two to three hours minimum to make sense of it all. Spring and autumn are lovely - fewer school groups and the weather won't exhaust you halfway round.

It slots perfectly into a caravan holiday near Southampton. Both Rookesbury Park and ScottsHaven are within easy striking distance, so you could base yourself at either and explore the fort without rushing. Pair it with a day at HMS Victory in Portsmouth, just down the road, and you've got a proper military-history break sorted.