Portaferry Castle

The castle sits right on the water's edge at Portaferry, a working 16th-century tower house that's still doing its job after five centuries. It's small - you won't need more than half an hour here - but it commands the narrow strait between Strangford Lough and the sea, which is precisely why it was built. The tower stands three storeys high with thick stone walls and genuine medieval charm, none of that over-restored feeling you sometimes get.

You can walk right up to it, and the views across the lough are genuinely worth the trip. On a clear day you'll spot Strangford on the opposite shore. History buffs will appreciate the defensive role it played; families with younger kids might find the exterior more interesting than any interior access, since there's not a great deal to do once you've climbed the stairs.

It's free to visit and accessible most of the time, though conditions can be a bit muddy underfoot. The nearest town is Downpatrick, about fifteen minutes' drive inland. If you're base camp is one of the caravan parks nearby - Castle Ward is closest at just over a mile - this makes for a brilliant short walk combined with exploring Strangford village itself, which has proper character and decent pubs. Don't expect a major attraction, but as a thirty-minute stop on a Ards and North Down loop, it's absolutely worth the detour. The light here in late afternoon is particularly good.