Poros is one of the Saronic Islands of Greece, located in the Aegean Sea between the Saronic and Argolic Gulfs. It is separated from the Peloponnese by a narrow strip of water. It consists of two islands, Sphairia in the south and Kalaureia in the north. The southern part is of volcanic origin and where the main town is located, whilst the northern part is the largest of the two. A bridge connects the two islands over a narrow strait.

In antiquity, the city-state of Calauria was home to an asylum dedicated to Poseidon, the ruins of which are still accessible on a hilltop close to the town. This asylum may have been linked to the sanctuaries at Geraistos and Tainaros. Ancient historians stated that Calauria was the center of an amphictyony, a religious alliance between its city-state and those of Athens, Poros, Aegina, Epidaurus, Hermione, Troezen, Nauplio, Orchomenus, and Prasaiai.

Nowadays, Poros is an island with rich vegetation. Much of the northern and far eastern/western sides of the island are bushy, whereas large areas of old pine forest are found in the south and center of the island. It has a good road network and adequate tourist infrastructure, which makes it a popular resort for short holidays, especially among locals.

Most of the island's bars and  restaurants are located in the main town of Poros. Many isolated beaches offer the opportunity for relaxation on either island, with the most prominent being Askeli and Kanali. Sightseeing opportunities include monasteries that can be reached via hiking trails, the Temple of Poseidon and the town's Archeological Museum.

Poros' close proximity to Athens makes it a preferred destination for locals, especially in the weekends. The best time to visit is in late spring – the sea has warmed up to feasible swimming temperatures and locals outnumber tourists – and early autumn, when most of the tourists have departed and the sea is at its warmest.

Poros is only accessible by fast ferry from Athens (only 1 hour away) as the island is too small to have its own airport. Scheduling a trip there can provide a lot of flexibility as there are several ferries available every day at frequent intervals.