Old Aker Church (Gamle Aker kirke) is Oslo's oldest remaining building and the only remaining church from the Middle Ages. It is assumed that it was built around the year 1150. It is a stone church, built as a three-naved Roman-style basilica.
The church has been pillaged and ravaged by fire several times. The oldest part of the surrounding churchyard dates back to the 12th century. The church has a baroque pulpit and baptismal font from 1715. The tower was built in 1861.
The church was built over an old silver mine, Akersberg which was in use since the early Viking age. The mines are mentioned in the 1170 Historia Norvegiae. The mines must have been the inspiration for a number of stories about the church having hidden silver treasures and even dungeons with dragons.
References:The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.