This was once a fire station. Since Bergen has always had large areas with wooden buildings, placing a fire station with a watchtower like this makes perfect sense. I have even shown pictures of this station before, but then from an other angle. The lake in front of the picture was to act as a water supply during fires.
The station has been out of use for a long time and is now used as a clubhouse for "Skansen bataljon" - a "buekorps" (a boy's brigade - a peculiar custom seen only in Bergen as far as I know). There are plans for filling in the lake and using it as an entrance for an underground parking lot for the people in the area. A thing not to popular among the historically interested people in Bergen.
5 hours ago