Castell Mawr

A hillfort that's genuinely difficult to reach - which is rather the point. Castell Mawr sits above Newport in Pembrokeshire, and you'll need to do some proper walking to get anywhere near it, scrambling up through scrub and bracken to find the Iron Age ramparts that still define the ridge. The earthworks are substantial enough to make you understand why someone chose this spot to defend, hundreds of years before the Romans showed up.

It's not a visitor attraction in the conventional sense. There's no car park, no interpretation boards, no one taking money at a gate. You just turn up and walk it, which means it rewards the kind of visitor who actually enjoys archaeology rather than just ticking boxes. Families with young kids might find it frustrating - the final approach is steep and muddy - but teenagers and proper walkers will get a real kick out of the scramble and the views across the Preseli Hills once you're up there.

Allow a couple of hours including the walk in and out from Newport. The best time is autumn or winter when the bracken dies back and you can actually see where you're going. If you're staying at Llwyngwair Manor Holiday Park just down the road, it's an excellent morning mission before lunch - far more engaging than the polished heritage sites that charge admission. Bring proper boots though. It's muddy.