Hydra, Saronic Islands in the context of "Provinces of Greece"

The Saronic Islands or Argo-Saronic Islands is an archipelago in Greece, named after the Saronic Gulf in which they are located, just off the Greek mainland. The main inhabited islands of this group are Salamis, Aegina, Agistri, and Poros. The islands of Hydra and Dokos, which lie off the northeast tip of the Peloponnese (technically between the Saronic Gulf and the Argolic Gulf), are sometimes included as part of the Saronic Islands.

Many mainland Greeks have vacation homes in the Saronic Islands, which are regularly served by ferries from the Athen's port of Piraeus and the Peloponnese. Salamis, the largest island of the group, is where the ancient Greek navy defeated the Persians in the Battle of Salamis in 480 BC.

Dokos (Greek: Δοκός) is a small Greek island of the Argo-Saronic Gulf, adjacent to Hydra, and separated from the Peloponnese by a narrow strait called, on some maps, "the Hydra Gulf." It is part of the municipality of Ýdra (Hydra) in Islands regional unit and reported a population of 18 persons at the 2011 census. The island is populated only by some Orthodox monks and perennial sheep herders. The island is rocky, reaching a height of 308 metres (1,010 ft).During ancient times it was called Aperopia (Ἀπεροπία).

Argolis and Corinthia Prefecture (Greek: Νομός Ἀργολίδος καὶ Κορινθίας), commonly known as Argolidocorinthia (Ἀργολιδοκορινθία), was one of the prefectures of Greece. Its capital was Nafplio. It was one of the first prefectures established, first in 1833–1836 and again from 1845 until 1899, when it was split into Argolis Prefecture and Corinthia Prefecture. The split was reversed in the 1909 administrative reform, and the prefecture existed until split again in 1947.

The northern half became Corinthia with its capital at the city of Corinth, the southern half became Argolis with its capital at Nafplio. The islands Hydra, Spetses, and Kythira in the south became part of the Attica Prefecture.