It is the largest island after Crete and Euboea in the Aegean Sea.
The island is largely volcanic in the west, and numerous thermal springs indicate the unstable subterranean structure that has caused severe earthquakes throughout history.
The irregular coast of Lésbos is penetrated by two narrow-mouthed bays, Géras (southeast) and the Gulf of Kallonís (southwest).
The principal peak is Mount Lepethymnus (Áyios Ilías) which reaches 3,176 feet.
