Akershus Fortress: A Historic Royal Stronghold and Military Site in Oslo, Norway
Visitor Information
Google Rating: 4.5
Popularity: High
Official Website: kultur.forsvaret.no
Country: Norway
Civilization: Early Modern, Medieval European, Modern
Site type: Military
Remains: Castle
History
Akershus Fortress is situated on the Akersneset peninsula in Oslo, Norway. It was constructed by the medieval Norse civilization, under the reign of King Håkon V Magnusson, in the late 13th century as a royal stronghold and residence.
The initial phase of the fortress dates from approximately 1287 to 1300 when King Håkon V replaced the earlier royal seat at Bergen with this new castle. Serving as the seat of Norwegian royal power, the fortress was both a residence and administrative center. Throughout the Middle Ages, it became a crucial military bastion, enduring multiple sieges. Notably, Swedish forces launched attacks in 1308, 1449–1450, 1502, 1523, 1567, and 1716, yet none succeeded in capturing the fortress, underscoring its strategic resilience.
During the 16th and 17th centuries, Akershus Fortress underwent significant transformation. Influenced by advancements in artillery and military engineering, particularly under King Christian IV, it was rebuilt and expanded into a Renaissance-style castle. Italian design principles were adopted to create bastion fortifications that strengthened its defensive capacity. Engineers Hans van Pæschen and Hans van Steenwinkel played key roles in these developments.
Over the centuries, the fortress served multiple roles beyond military defense. It functioned as a prison, gaining a reputation in the 19th century as Norway’s strictest correctional facility. During World War II, under German occupation, the fortress again operated as a prison and site for executions, particularly targeting political prisoners and war criminals.
Following its military decommissioning in the 19th century, extensive restoration projects were initiated from the late 1800s through the mid-20th century. Leading architects including Wilhelm von Hanno, Heinrich Ernst Schirmer, Peter Andreas Blix, Holger Sinding-Larsen, Arnstein Arneberg, and Johan Adolf Gerhard Fischer contributed to preserving the medieval and Renaissance fabric of the site while adapting it for contemporary use. In addition to military functions, parts of the fortress today accommodate official government ceremonies and house museums dedicated to Norwegian military history.
A notable feature within Akershus is its royal mausoleum, located in the crypt of the castle church. It contains the remains of significant modern Norwegian monarchs such as King Håkon VII, Queen Maud, King Olav V, and Crown Princess Märtha, alongside medieval royal relics, linking the fortress intimately with Norway’s royal heritage.
Remains
Akershus Fortress spans roughly 17 hectares (170 decares) and comprises three main components: the medieval core castle, the surrounding inner bastion fortress, and the outer fortification zone. The complex is built primarily of stone and brick, with structures dating from its original medieval construction through Renaissance expansions and later military additions.
The medieval castle forms the heart of Akershus, featuring several key wings and towers constructed around 1300. Among these are the Nordfløyen (North Wing), which housed the royal hall and chambers, and the Vågehalstårnet, a central keep tower originally about 20 meters tall but partially demolished following a fire in 1527. The Knutstårnet, formerly known as Kanniktårnet, served as a northern defensive tower and was rebuilt after fire damage. The Sydfløyen (South Wing) includes the castle church and royal apartments, while the Romeriksfløyen (Romerik Wing) was dedicated to kitchen and administrative spaces. Administrative functions were further supported by the Skriverstuefløyen (Scribe’s Wing), complemented by the Fruerstuehuset (Women’s Wing). Additionally, the Jomfrutårnet (Maiden Tower) served as an outer gate tower featuring remnants of its original drawbridge and portcullis, pointing to its role in access control.
The Renaissance era brought significant defensive upgrades influenced by Italian military architecture. Bastion fortifications were added around the medieval core, including earthwork batteries such as Dronningens batteri (Queen’s Battery) and Kongens batteri (King’s Battery), both equipped with casemates and cannon openings. The Skarpenort Bastion stands out with its large powder tower, known as Skarpenorts kruttårn, used for storing gunpowder securely. Further bastions such as Kronprinsens bastion (Crown Prince’s Bastion), Prins Carls Bastion, and the Hornverk (Hornwork) include stone-faced defensive walls and casemates constructed from local stone and bricks salvaged from the ruins of the nearby Hovedøya monastery. Walls here reach thicknesses of up to three meters, demonstrating adaptations to withstand artillery strikes. Several underground communication tunnels, named Lønngang and Mørkegang, allow protected movement within the fortress grounds.
The outer fortification area known as Hovedtangen encompasses additional bastions, earthworks, and military buildings erected primarily in the 18th and 19th centuries. These include the Myntens bastion (Mint Bastion), various stables designated for cavalry, engineers, and artillery units, as well as barracks and arsenals. Specialized structures further support the fortress’s military and administrative functions. The Artilleribygningen (Artillery Building), built in 1774, was central in gun storage and maintenance. The Kornmagasin functioned as a granary before reuse as a prison facility. The Fengselskirke (Prison Church), completed in 1866, served incarcerated individuals, while the Corps de Garde (guardhouse, 1754) and Laboratoriekjøkkenet (Laboratory Kitchen, 1836) are further examples of purpose-built annexes.
The castle church located in the South Wing contains a crypt that houses the royal mausoleum. Here, marble sarcophagi hold modern Norwegian monarchs alongside medieval royal relics embedded within the walls, preserving an important link to Norway’s dynastic history.
The main fortress gate, Festningsporten, was finished in 1653. It features a bridge crossing Kongens gate and displays King Christian IV’s monogram. Over time, this gate has been rebuilt several times, reflecting changes in defensive needs and architectural styles.
The fortress grounds also include open spaces like the Kontraskjæret park and Festningsplassen parade ground, which have historically hosted military ceremonies. Today, many of the fortress’s walls, towers, and interiors have been restored or carefully reconstructed based on archaeological research, preserving both medieval and Renaissance elements. Akershus remains an active military site, supporting the Norwegian Armed Forces and housing important museums that document the nation’s defense history.