Kythera has an area of 284 km². It is 29 km long (N-S) and 18 km wide (E-W). The island is part of the same tectonic unit as the area that includes Macedonia, Thessalia, Sterea Hellas, Peloponnese and Crete. Its major features include hills and sheer cliffs. There is also a valley towards the east. Kythera belongs to the Alpine chain and more specifically to the southern branch of the Tethysian realm (Papanikolaou, 1986). The southern branch of the Tethysian realm includes the southern Alps, the Apennines, the Dinarics, the Taurids, the Iranids, as well as parts of other chains that touch the Himalaya.
The geological bedrock of Kythera is formed by the tectonic units of Arna, Tripolis and Pindos. Only the eastern part of the island is formed by more recent deposits.
Geological map of Kythera (Greek Institute of Geological Studies 2001 Ι.Γ.Μ.Ε)