The Blue Cave is a well known cave in the municipality of Anacapri, on the island of Capri near Naples. The Cave has an opening partially submerged and, depending on the tidal cycle, the access can be more or less complicated. The Roman emperors who spent their holidays on the island used it as a private swimming pool: it seems that Tiberius had built a direct passage to connect his villa with the Cave. Note from 1826, when it was visited by the German artist August Kopisch on the recommendation of Angelo Ferraro, a local fisherman. The most fascinating feature of the Blue Cave is the particular play of colors created by the external light penetrating through the submerged part.