Antrim Castle

The ruins sprawl across a decent chunk of parkland just outside Antrim town, and what you're looking at are the remains of a seventeenth-century castle that's seen better days - literally crumbling in places, but that's rather the point. Built in 1662, it got hammered during the 1798 Rebellion and never quite recovered, though the grounds themselves are worth an hour's wander regardless of the state of the stonework.

History buffs will find the bones of it interesting enough - you can make out the main structure, some of the internal walls, and get a sense of how imposing it must have been. Kids tend to enjoy scrambling about on the ruins, though parents will want to keep an eye on loose stones. The surrounding park is actually pleasant, with decent walking paths and open grass areas, so it's not a case of turning up, looking at a pile of rocks for ten minutes, and leaving.

The whole thing is free to access, and there's no time restriction really - turn up when you fancy it. Early morning or late afternoon tends to be quieter. Given that Six Mile Water Caravan Park is barely half a mile away, and Blair's Castlewood is even closer, it makes sense to throw this into a broader park-based holiday in the area. You're not going to spend the full day here, but it's a solid spot for a midday leg-stretch before heading back to your pitch for dinner.