Pianosa is a small (about 10 km2) island in Italy's Tuscan Archipelago. The name is derived from the latin word "planasia" (plain) because its highest point is some 22 meters over sea level. Pianosa has no permanent residents. It is known in Italy for a maximum-security prison, where especially dangerous Mafia criminals are held. For administration, Pianosa is part of the Elba island municipality. On clear days, it can be seen from that island as a dark blue line over the lighter blue sea.
There is another, even smaller island called Pianosa off the Adriatic coast of Italy.