Smoo Cave, located in Durness, Scotland, is a unique sea and freshwater cave formed in dolomites. The name "Smoo" is believed to come from Norse origins meaning a hole or hiding place. The cave features a large sea cave entrance chamber, a waterfall chamber, and a freshwater passage leading to a terminal sump chamber. Archaeological findings suggest Neolithic, Norse, and Iron Age artifacts were found in the cave, with evidence of Viking/Norse or medieval activity. With around 40,000 visitors annually, Smoo Cave offers tours during the summer, taking visitors to the inner chamber by boat.