The island of Jurmo in the outer archipelago is the largest of a number of islands which belong to the magnificent Salpausselkä ridge, one of the biggest territorial moraines in Northern Europe stretching from Karelia in the east to the Hanko area in south-west Finland. This five kilometer long barren island, with an unusual plant life, is mentioned in a document as early as 1270. No trees grow on Jurmo, save a small number of planted pines and a few birches and alders in a marsh. According to an oral tradition, there used to be a pine forest on the island but in the 16th century it was burned down by a Swedish expedition sent to punish the local inhabitants, who had been accused of piracy.

Archipelago National Park

Until fairly recent times Jurmo did not have a proper sheltered harbor, which made access to the island difficult. Now there is a pier that protects visiting ships and boats and the island also offers other facilities for seafarers during the summer months. Jurmo is now part of the Southwestern Archipelago National Park. Visitors without a boat of their own can easily board a supply ship that maintains a regular service between Jurmo and the main islands that are accessible by car or bus.