The unique Smoo Cave in Sutherland, Scotland is a really cool natural attraction. The cave was formed by a combination of rainwater dissolving carbonate dolomites and erosion from the sea. It is composed of three main sections: a large sea-cave entrance chamber, a waterfall chamber, and a short freshwater passage with flowstone formations at the rear.

Reaching here is a short walk from the car park, but does require good footwear and waterproof clothing as it gets quite wet around the waterfall!