Biskopsö 59,6,4 N - 18° 43,8 E

In the early years of the 20th century a new era began in the archipelago. Wealthy Stockholm businessmen and artists turned to the archipelago for a life in the summer near nature and for hunting. Year 1917 two cottages were built on Biskopsö and from then on the island has had permanent residents. The owner is "Biskopsöstiftelsen" a foundation founded by the late owner, Marcus Wallenberg.

Plenty of details around the old history is unknown but it is known that the waters south of Biskopsö were rich with fish. There were fishing cabins both on Byttan and on Finnskär. Fishing rights were purchased by nearby homestead Gillinge on 1859. The meadows - that used to be harvested for hay by the homestead - is now restored and maintained, since Biskopsö now is a nature reservation.

Biskopsö is in the outer archipelago, about 15 km east of Ornö. The exposed location has formed both plants and animals to suit life close to the sea and wind. The smaller skerries are almost without any vegetation, while the larger islets, like Kastön have the vegetation so typical for the outer archipelago; - low pines and junipers, heather and blueberries.

The main island, Biskopsön, has a much more varied vegetation with both birch, salix and aspen. The vegetation bears strong signs from being used by the deers brought to the island in 1920s. The deers now number around 50.. The almost extinct seal has an important habitat at Själberget and the surrounding skerries.