In the 8th century, a settlement was built right at the top of the Oslo Fjord. This little Norwegian village grew rapidly during Viking times: agriculture, trade and shipbuilding were important commercial activities, and Oslo has truly earned its title of "Viking Capital".

Oslo was founded long after the town had been developed by the Vikings. According to the Viking sagas, the city of Oslo was founded by King Harald Hardråde in approximately year 1050 AD. More recent archeological findings, however, prove that the city was founded as far back as in 1000 AD. The founding of the city took place in the turbulent period between the Viking Age and Norway's Catholic Middle Ages.

Many remnants and ruins from Ancient Oslo can be found in the Memorial Park. The city had a fascinating, interesting and dramatic history. Oslo´s population was substantially reduced during the time of the Black Death in 1348 which claimed over 50% of the inhabitants. This epidemic also had political consequences for Norway, which became reduced to a province of Denmark. During this period Copenhagen was the actual capital of Norway.

Oslo was also greatly affected by the Lutheran-Protestant Reformation of 1537, with religious conflicts, political separation from the Catholic Church and the foundation of a Protestant National Church. Many ruins of churches and monasteries (for example Cistersienserklosteret - the Cistercian Abbey - at Hovedøya) bear witness to this process.

Oslo was completely destroyed by fire in 1624. The Renaissance King, Christian IV of Denmark and Norway, decided to move Oslo from what we today call the Old Town, and rebuild it under the protective shadow of Akershus Festning (Akershus Fortress). Following intense renewal work and advanced city planning in the spirit of the Renaissance, a completely new city was created and named Christiania in 1624.

After 1814 Norway was united with Sweden, and Christiania experienced very strong economic and political growth with substantial expa sion right up until the dissolution of the union with Sweden and independence in 1905. After the celebration of the 300th anniversary of Christiania in 1924, it was decided that the original name of Oslo was to be re-instated as of January 1,1925.