Along with the nearby islets Prasoudi, Planemi and Agios Ioannis comprise a small group of islands.

It is located off the north coast of the Corinthian gulf, opposite the villages Glyfada and Chania of Phocis prefecture.

According to a view, the name derives from the small insect cricket (in Greek trizoni).

[5] The biggest of them is named Pounta (also known as the red beach) and is located in the south of the island, with a view of the Peloponnesian coast, Aigio and the Rio–Antirrio Bridge.

Edward Blaquiere, a former lieutenant in the Royal Navy and a well known philhellene of his time, visited Trizonia in 1825 and he mentions a ruined village.