What is "sideros"

Sideros (, "iron"), also known as Strongylo (, "round"), is an uninhabited Greek rock, in the Aegean Sea, close to the northeastern coast of eastern Crete. The rock lies just north of the peninsula of Kyriamadi, with which it is connected by a small land bridge. There is also a Cape Sideros on the island of Kyriamadi. Administratively it lies within the Itanos municipality of Lasithi.