The word Poros is a geographical term that means a small sea strip which connects two small bays. Indeed, the distance between Poros and the coast across, in the nearest point is only 200m. The ancient authors initially mentioned Poros with the name Irini (peace) probably, because of the peace that dominated the area after the Dorian descent and the disruption of the Mycenaean state.

Poros consists of two islands, which come from two different geological periods, Sphera and Kalavria. Sphera owes its name to Spheros who was buried in the island. Later it was renamed to Iera.

The second island was named Skelerdia and Kalavria, when the town was built around the sanctuary. Kalavria means, good breeze. Maybe, it took this name from Kalavropa Apollo who was worshiped in the island.

Poros covers a distance of 31,3 sq. Km., and population of 4,000 people. It is situated 32 nautical miles from Piraeus. The town is built on two rocky hills of a triangular islet that is called Spheria and it has been characterized as a scheduled settlement. The houses, without any specific architectural plan, are built one next to the other.

The Albanians from the Peloponnese built the first settlements in Casteli. Chased by the Turks they found refuge in this area, in 1463. The small but interesting Archaeological Museum of Poros is situated in Korizi's square.

It exhibits findings from the ancient Kalavria and the ancient Troizina. Most of the visitors make the tour of Spheria using the circular road of the island.

Poros has a developed tourist substructure. Modern hotels and rent rooms will serve the visitors. The port of Poros, the center of life of the island, presents a bright and pleasant sight with the anchors, the cannons and the marvelous shops. A festival that no one should miss is the nautical week, which is organized during summer months.