Suomenlinna (Finnish) or Sveaborg (Swedish), until 1918 Viapori (Finnish), is an inhabited sea fortress built on six islands (Kustaanmiekka, Susisaari, Iso-Mustasaari, Pikku-Mustasaari, Länsi-Mustasaari and Långören) and which now forms part of the city of Helsinki, the capital of Finland.