The history of Oslo begins in the Middle Ages; the first town-like settlement probably appeared around the year 1000 AD. The medieval town was located below the Ekeberg hills, on the east side of the Bjørvika inlet, in the area today called Gamlebyen (Old Town).
Around the year 1300 AD, the population of Oslo was approximately 3000. King Håkon V (1299-1319) was the first king to reside in Oslo. The medieval town had six churches - the most important were the Maria Church and St. Hallvard's Cathedral. There were also three convents in the city and one on the island Hovedøya. The building of Aker Castle and Fortress (later called Akershus) was commenced by Håkon V.
Remains of medieval Oslo are found in Gamlebyen, in the form of ruins, building parts and cultural layers. Here you also find Oslo Ladegård's Medieval Office, that can help you with information about medieval Oslo or a guided tour in the ruin park.
The Aker estate and Old Aker Church (Gamle Aker kirke) was a religious centre. This was also were the thing (the governing assembly) was located. The church is located just north of today's city centre - in the Middle Ages is was outside the town.