The extraordinary Kastania Cave located at the end of a spectacularly winding 17km route northeast of Neapoli, contains some of the best examples of rare stalactites and stalagmites in Europe, estimated to be around 3 million years old. Guided tours in English depart hourly; as you walk around a raised and lit 3km circuit, guides are quick to point out octopi, exotic plants and otherworldly creatures cast in stone. Call ahead to double-check opening times.