Killingen is a small island in the Oslofjord, just west of the Bygdøy peninsula in Oslo. The island covers about 92 dekar and today hosts a marina and small-boat harbor, with docks linking it to Bygdøy so that it is effectively connected to the mainland. Killingen has a long history: on its eastern side once stood a boatyard (Herberns Baatbyggeri) that built sailboats, and in 1923 the strait between Killingen and Bygdøy saw a violent clash between alcohol smugglers and police. A northern part of the island (Vesle Killingen) was later declared a geological natural heritage site because of fossil-bearing rock formations, and in 2012 the entire island was officially protected as part of the conservation of Bygdøy.