Bastion 5, Hilsea Lines

You're standing on what amounts to a Victorian military panic attack in brick and earth - Bastion 5, part of the Hilsea Lines fortifications that ring Portsmouth. Built in the 1860s when everyone was worried the French might actually invade, it's one of the few remaining bastions you can still access and poke around.

What you get is archaeology meets military engineering. The bastion itself is a proper earthwork with traces of the gun emplacements and barracks still visible, though nature's doing its best to reclaim the lot. It's not a manicured heritage site with plaques and reconstructions - it's more a case of reading the landscape and imagining what went on here when soldiers were drilling on the parade ground.

This works best for history types and walkers who don't mind a bit of detective work. Kids might find it dull unless they're genuinely into forts and fortifications. Allow an hour at most, though you could easily spend twenty minutes and be done with it.

Stay at Hayling Island Holiday Park or any of the touring parks nearby - Mill Rythe Coastal Village and Fishery Creek are all within a few miles - and you can combine this with a beach day without it being much of a drive. Bastion 5 is a decent add-on to a coastal holiday rather than a destination in itself. Free to access, naturally, since it's basically walking around an old earthwork.