The peripheries (περιφέρειες) are the official regional administrative divisions of Greece. There are 13 peripheries (nine on the mainland and four island groups), which are further subdivided into 54 prefectures.
In addition to these there is one autonomous region, Mount Athos (Ayion Oros, or "Holy Mountain"), a monastic state under Greek sovereignty. It is located on the easternmost of the three large peninsulas jutting into the Aegean from Central Macedonia periphery.
The periphery of West Greece consists of two geographically distinct exclaves, the northern one comprising the prefecture of Aetolia-Akarnania in geographical West Central Greece and the southern one comprising the prefectures of Achaea and Elis in geographical Northwest Peloponnese. They are separated by the Patraic Gulf and, in terms of transportation, adjoined by the Rio-Antirrio bridge.
Troizina is an exclave of the periphery of Attica (the prefecture of Piraeus in particular) on the northern coast of geographical Argolis, bordering the periphery of Peloponnese (the prefecture of Argolis in particular) on the south
Central Greece (with the exception of the province of Domokos of the prefecture of Phthiotis; contrariwise, the prefecture of Phthiotis also originally included within its limits, at its very northeast, a small area containing the town of Amaliapolis, that after the annexation of Thessaly in 1881 became part of the prefecture of Magnesia of the current periphery of Thessaly)
