Its name comes from the Italian pianura (plain). Its highest point stands 22 m (72 ft) above sea level. Pianosa is part of the Elba island municipality. On clear days, Elbans see Pianosa as a dark blue line over the lighter blue sea.
Pianosa was the site of a maximum-security prison (1858–1998), in later years holding especially dangerous Mafia criminals, although the island is not now inhabited for the whole year. It is part of the National Park of the Tuscan Archipelago.
It is a Marine Protected Area — no fishing, diving or anchoring is allowed without special permit. During tourist season it is connected by boat to Elba. Cell phones do not work on the island.