According to Greek mythology, the island was formed when Poseidon cut off a part of Kos and threw it onto the giant Polyvotis to stop him from escaping. The ancient name of the Nisyros was Porphyris.
Ancient walls, dating from the 5th century BC, part of the acropolis of the island, are found near Mandraki.
The island is reachable by ship from Piraeus and Kos, and in summer, there are many daily trips from the village of Kardamena on Kos.
The main town and port of the island is Mandraki