Holmen (Danish: The Islet) is a water-bound neighbourhood in Copenhagen, Denmark, occupying the former grounds of the Royal Naval Base and Dockyards. In spite of its name, deceptively in singular, Holmen is a congregation of small islands, forming a north-eastern extension of Christianshavn between Zealand and the northern tip of Amager.
Holmen was created by a series of land reclamations to house the Holmen naval base after it was moved from Gammelholm and used to occupy the entire area, but activities have gradually been moved elsewhere. Since the early 1990s, the area has instead been redeveloped for other use as a new district of the city, while the remaining naval facilities are confined to the northernmost islet of Nyholm. The area is today characterized by a mixture of residential developments, creative businesses and educational institutions and remaining military activities. Holmen is also home to the Copenhagen Opera House which was completed in 2005.
In 1680, a plan was conceived to move the fleet out of the city. Responsibility for the plan was given to Admiral Niels Juel.
She was built as a Type 207 submarine by Rheinstahl-Nordseewerke of Emden, Germany in 1965 for the Royal Norwegian Navy and served for 25 years as HNoMS Uthaug before being purchased by Denmark in 1990, and renamed after the seal. Her international call sign is OUCJ.
On 4 December 1990, Sælen sank while being towed from Copenhagen to Aarhus. On 17 December, she was raised by the German floating crane Roland and taken to Aarhus for repair. On 10 August 1993, diving approval was issued and the boat was recommissioned.
Sælen served in the 2003 invasion of Iraq from May 2002 until June 2003. To speed her return to her homeport of Frederikshavn after 385 days of deployment in the Mediterranean Sea and the Persian Gulf, she was transported on board the heavy-lift ship Grietje.