Cannonball in Tollbugata in Sentrum, Norway

During the 11-years war between Norway and Sweden (1709–1720), Oslo (then Christiania) was invaded. The Norwegian forces let the Swedes take the city, and retreated to the highly protected Akershus Fortress. 

Despite their best efforts, the Swedes were not able to capture the fortress due to heavy fighting. It was during this period of intense fighting that a cannonball from Akershus was fired and got implanted in the wall of a building on the corner of Tollbugata and Dronningens st. Although this building was eventually torn down, the current building, from the early 1900s, had the cannonball mounted in the same spot.