Ogof Pen Trwyn

Dark limestone walls stretch into blackness as you squeeze through the narrow entrance to this coastal cave system on the Great Orme. Ogof Pen Trwyn translates as 'Cave of the Headland', and that's exactly what you get - a proper underground adventure carved by centuries of pounding waves just outside Llandudno.

Serious cavers rate this one highly, though it's definitely not for claustrophobes or anyone expecting a gentle stroll. You'll need a torch, old clothes you don't mind getting muddy, and a reasonable level of fitness. The passages twist and turn through the limestone, with some tight squeezes that'll have you crawling on your belly.

Families with young children should probably give this a miss - it's more suited to adventurous teenagers and adults who fancy a bit of underground exploration. The reward comes in the form of stunning rock formations and the thrill of proper caving without needing to travel to the Yorkshire Dales.

Location-wise, it's a cracking addition to a North Wales break. If you're staying at one of the holiday parks near Llandudno like Hafan y Gogarth or Aberconwy Resort, it's an easy drive to the Great Orme. Just don't expect facilities or guided tours - this is wild caving at its most authentic.