The picture shows the two volcanic formations called La Canna (left) and Montenassari (or Monte Nassari).
Montenassari is a small islet, northwest of Filicudi, set on a depth of about 20-25 meters in depth.
A natural pool filled with sea water lies in the side of montenassari to the island of Filicudi.
This pool is connected to the opposite end of the islet through a submarine cave a few meters to the nearest point.
From Montenassari you can see the ancient villages of Ficarrisi, Siccagni, Giacomo Rock, La Canna, and Perciato.
At the top of Montenassari there was placed a small solar-powered lighthouse that automatically turned on at dusk.
Here's another picture of Montenassari.