A small island in the Venetian lagoon with one of the darkest histories in Italy: a quarantine station for plague ships, where the sick and dying were sent, and later a mental asylum. It is said the soil is half ash. The island is CLOSED to the public and landing is prohibited, so this is one to know and read about, not to visit; you can see it from the water on the way to the southern lagoon.
Poveglia island, the Venetian Lagoon (Italy)
See it on the map
Other places on the map within a couple of hours.