Ariel Cave (Blacknor Hole), Queens Entrance

The entrance to Ariel Cave sits on Portland's rocky coast, a proper scramble down to reach it. Once you're at the Queens Entrance - named after a royal visit years back - you're peering into a limestone cavern that's been carved by the sea for millennia. The cave itself doesn't run deep, but that's rather the point. This is about the geology, the sound of water echoing off stone, and the slightly illicit thrill of clambering about where few tourists bother.

It's a solid hour's outing if you're exploring the caves of Portland properly - there are several to hunt down in this area, and Ariel Cave is one of the more accessible. Bring proper footwear though. The rocks are slick, uneven, and the tide matters here. You'll want to check timings before you go, as access depends entirely on sea levels. Free to visit, which helps.

Walkers and geology enthusiasts will find this rewarding. Kids can manage it if they're steady on their feet and not afraid of tight spaces. Families based at Chesil Beach Lodge Park - just 4.5 miles away - could easily make this a morning adventure. The caves feel like a proper secret in amongst the holiday parks and beach tourism of Weymouth. It's not Instagram-friendly, which is exactly why it's worth the detour.