Bastion 3, Hilsea Lines

The Victorian military engineering at Hilsea Lines is proper impressive if you're into fortifications and 19th-century defensive strategy. Bastion 3 is one of several bastions that make up this impressive ring of earthworks built between 1860 and 1880 to protect Portsmouth from a French invasion that never came. You're essentially walking around grassy ramparts and examining the geometric precision of Victorian military architecture - angular bastions, ditches, and raised gun platforms that sprawl across several acres near Hayling Island.

History enthusiasts will spend a good couple of hours here poking around the various positions and trying to imagine the garrison life. The scale of the earthworks is genuinely striking when you're stood on them - this wasn't a rushed job. Families with older kids might find it interesting, though there's not much in the way of interpretation boards or visitor facilities, so younger children could lose interest fairly quickly. Walking boots are sensible; the ground gets muddy after rain.

If you're based at one of the caravan parks on Hayling Island - Hayling Island Holiday Park or Mill Rythe Coastal Village are closest at four to five miles away - this makes an easy detour on a decent day. It's free to access and you can turn up whenever you fancy. Allow an hour minimum if you're just doing a quick walk, but give yourself two hours if you want to explore properly and actually work out which bastion is which. It's not a standalone day out, but it sits well alongside a beach trip or a walk along the seafront.