Acrocorinth

"[1] With its secure water supply, Acrocorinth's fortress was repeatedly used as a last line of defense in southern Greece because it commanded the Isthmus of Corinth, repelling foes from entry by land into the Peloponnese peninsula.

Along with Demetrias and Chalcis, the Acrocorinth during the Hellenistic period formed one of the so-called “Fetters of Greece” – three fortresses garrisoned by the Macedonians to secure their control of the Greek city-states.

The city's archaic acropolis was already an easily defensible position due to its geomorphology; it was further heavily fortified during the Byzantine Empire as it became the seat of the strategos of the thema of Hellas and later of the Peloponnese.

In a Corinthian myth related in the 2nd century CE to Pausanias, Briareus, one of the Hecatoncheires, was the arbitrator in a dispute between Poseidon (the sea) and Helios (the sun): His verdict was that the Isthmus of Corinth belonged to Poseidon and the acropolis of Corinth (Acrocorinth) to Helios.

The latter knew, so runs the legend, that Zeus had ravished Aegina, the daughter of Asopus, but refused to give information to the seeker before he had a spring given him on the Acrocorinthus.