The Grotta dell'Arsenale is a cave on the island of Capri, southern Italy. It may have been used in the time of Roman emperor Tiberius as a depot for naval stores. It measures 4 m long by 3.5 wide by 1.5 m high. Excavations made in 1777 in the shingle, which still covers the floor to a depth of from 1.2-1.5 m, showed evidence of traces in the walls of two or three rooms which were of Roman workmanship, along with a floor of coloured marbles, and some iron fragments, which have been identified as part of the plant of the ancient naval station, or perhaps of a Roman galley. Although the floor of the cave is 2.4 m above the sea, in southerly gales, waves hit it so forcefully as to render its use as a storehouse out of the question. The walls unearthed here indicate, therefore, that at the ti