The history of Oslo begins in the Middle Ages; the first town-like settlement probably appeared around the year 1,000 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).

The park was built in 2000 in Sørenga, Gamlebyen (The Old Town). It is located within the Medieval Park area, which also includes the Memorial Park and Ladegården on the north side of Bispegata. In this area, development is not allowed due to the ruins and plenty of cultural remains in the underground.

St. Mary`s Church ( From the early 1100s to 1542):

Excavations were first conducted in 1867  and later in the 1960s

St Mary`s was one of the most beautiful churches in Norway in 1300. Located immediately adjacent to the King`s Residence, St. Mary`s was a royal chapel.

Remains of two people, deemed to be King Haakon V (died 1319) and his Queen consort Euphemia of Rügen, were discovered during excavations of the ruins of the church and re-interred in the Royal Mausoleum in Akershus Castle 

Traces of an older wooden structure (a stave church) built in about 1050, were discovered. Logs are placed in the ruins to mark the traces.  The stave church was replaced by a stone church in about 1100.

About 1300s under the rule of Haakon V, the church was rebuilt in brick.  There was a fire in the church in 1523, and by 1542 it was so dilapidated that it could no longer be repaired

A reconstruction suggestion on how St. Marys looked like (the year 1300) based on the excavations: