This is an old lock in 脜kers kanal, an old waterway in the Stockholm suburb 脜kersberga.
It was built in 1825 and the land raising of the area had made the old river impassable.
Land raising?
Yes, during the ice age Sweden was covered by a kilometers thick layer of ice, which pushed the crust of the planet at that point down into the core. The land raising is just the process of the plates slowly resetting.
It has been found that at about 10 300 years ago, the local area was 150 below the current sea level.
As the ice melted the land rose up very fast at first, in some places at 250m/year.
In the last several centuries, the land raising have only really been at a few mm per year, yet it still continues to this day.
There are som interesting examples of this phenomenon, 脜kers kanal is one, another is that the city of Stockholm had to lower the docks in parts of the city by half a meter to get them back to the same height above the water as they had when they had 100 years ago.
Now, back to 脜kers kanal, there used to be passenger and cargo traffic on the canal, but over time the local railroad, Roslagsbanan, and even later, cars took over that business.
These days the canal is maintained for leisure use, but no commercial traffic passes along it.
The lock is still maintained, and in use, I mainly use it to walk a cross the canal and get to the bus to get to work.
This photo was taken in 1951 and is in the public domain.