Church of the Cross was a small medieval parish church for the northern part of the Old Town of Oslo. The ruin was rediscovered in 1922 and is now a part of the Ruin Park containing the ruins of the church and the greater St. Hallvard's Cathedral.
There is no definite information about when the church was built. The church is not mentioned in the sources of the fighting in Oslo in 1240 between King Haakon IV and Duke Skule, suggesting that it is possibly younger. In 1989 it was found a stick with runic inscriptions, dated to the first half of the 1200s. The name Church of the Cross occurs in this inscriptions, and it indicates that it may be older than 1240. When the church was built, it was located far north in the city, and an urban development north of the church came in the second half of the 1200s and the 1300s.
Church of the Cross had input from the west, from the cemetery, an entrance from the west and an entrance directly to the chancel from the south. The remains of the original altar foundation is visible. Around the church are the remains of the cemetery wall.
References:The Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.