Tucked into the rugged cliffs west of Xlendi Bay, on Gozo's wild southern coast, L-Għar ta' Santa Katarina — Saint Catherine's Cave — is one of those places you only ever stumble on from the water. There's no path down and no sign pointing the way: you rent a kayak or paddleboard in Xlendi and follow the cliffs for fifteen or twenty minutes until a gargantuan cavern opens up ahead, complete with its own little rock beach hidden inside. The rock here is raw and weathered — nothing like the smooth pale grottoes elsewhere on the island — and the water glows an unreal turquoise beneath the arch. It's a dream spot to swim, snorkel the small reef and canyon along the edges, or scramble up the pitted ledges for a cliff jump into the deep blue. Look closely at the walls and you'll find graffiti carved into the rock a century ago by earlier visitors. Bring everything you need — there are no facilities out here — pick a calm day, and keep an eye on the swell and wind before you set off.