Photo: trolvag·CC BY-SA 3.0· Wikimedia Commons
Islands / Horten / Mellomøya
Mellomøya is an island near Horten that the Norwegian Navy used for ammunition storage and TNT production; several military buildings still stand. The eastern part, towards Strømsund, is a plant conservation area for the rare violet *lodnefiol*.
Mellomøya is the low, elongated island in the naval area east of Horten, between Løvøya and Østøya, with bridges to both neighbours. The highest point, Masteberget, is 34 metres. The navy's powder magazine and explosives production were here, and several of the military buildings still stand among the trees.
Plant conservation area (*lodnefiol*), established 2006. The boundaries and the rules are in Naturbase, and they are worth checking before you land anywhere outside the marked areas.
Military heritage area; check access.
No scheduled boat comes here. You will have to find the nearest public quay yourself, and the rest is your own boat or a kayak. Check the wind and wave forecast before you set out; the open stretches in the outer fjord turn unpleasant in a fresh breeze.
The navy bought the island in 1819 from Falkensten Bruk. It was called Midtre Løvøy then; the Norwegian Mapping Authority (Kartverket) approved the name Mellomøya in 1966. For more than 150 years the island was used to store ammunition and to produce TNT. The installation consisted of a powder magazine, an ammunition magazine, an explosives magazine and a TNT works building (*trinolarbeidshus*), linked by a narrow-gauge railway. Under the German occupation from 1940 to 1945 the same kind of operation continued.
The explosives years are still in the ground. Sediment samples in 2011 showed elevated copper concentrations, while later seaweed analyses found no ongoing leaching from land.
The island is still inside the armed forces' area. The eastern part towards Strømsund became a plant conservation area (*plantefredningsområde*) on 30 June 2006, with 13 hectares protected for the nationally rare and threatened violet *lodnefiol* and its habitat.
Mellomøya lies in a military heritage area with restricted access, so check before planning a landing. On protection: the plant conservation area in the east dates from 30 June 2006 and was established for *lodnefiol*. Movement on land inside the protected area has to take account of the protected flora. There is no public ferry.
*Lodnefiol* on the east side is rare enough in Norway that 13 hectares were set aside for it. On an island known for its ammunition magazines, the formal grounds for protection are botanical.
The island made its own explosives. A dedicated works building produced TNT for the navy.
A narrow-gauge railway carried the ammunition between the magazines on the island.
Oslo Sea Experience passes Mellomøya on its private fjord trips from Tjuvholmen.
The Norwegian version notes which facts were taken from each source: Mellomøya på norsk.