St Catherine's Fort

The squat stone fort sits on a headland just off Tenby's coast, accessible via a causeway that's only passable at low tide. Built in the 1760s to defend against French raiders, it's a proper little fortress with thick walls and bastions commanding views across Carmarthen Bay. You're looking at maybe 45 minutes wandering round the gun emplacements and interior rooms - longer if you're the type to read every historical panel.

It's genuinely worth the walk from Tenby's seafront, though do check the tide tables before you head out or you'll be stranded. The views alone justify the trip - on a clear day you can see right along the coast. History buffs will appreciate the military engineering, but families with restless kids might find it a bit sparse after the initial excitement of the causeway crossing.

The fort pairs well with a park holiday around here. Saltern Holiday Park is barely half a mile away, while Haven Kiln Park and Becks Bay Camping are both close enough for an easy morning trip. Combine it with a proper wander round Tenby's medieval town walls and you've got a solid half-day. Just bring decent shoes - the approach path can be muddy and the causeway itself is uneven stone.