The Spandau Lock is in Berlin, in the district Spandau. It helps ships to cross from the Lower Havel (Untere Havel) into the Upper Havel (Obere Havel) despite their different water levels.
The history of the lock in Spandau begins around 1258 when the first mills were built around here. With the help of a dam, different water levels were created on either side of it and the drop between them was used to run the mills.
Over the years an array of different mills sprung up in Spandau, flour and oil mills as well as boring and grinding mills for the production of weapons. The sawmill in Spandau was so cutting edge at the time that it was used as an example for other mills that were constructed in the area.
But keeping the shipping traffic running at the mill dam in Spandau was only possible by unloading the goods from one ship and then loading them back onto another
Only after the addition of a flood channel ships were able to cross from Lower Havel to Upper Havel by themselves. The construction was authorized when Spandau was granted town privileges. The flood channel split the Havel Island into two parts, the northern part Zitadelleninsel (Citadel Island) and the southern part Altstadt (Old Town). The headwater was regulated with a weir. If opened quickly ships could ride the wave into both directions. Ships travelling upstream had to be towed in addition to the force of the wave.
The first lock in Spandau was created in 1572. It was a chamber lock. It was modernised multiple times over the years and in 1875 it was made big enough for ships with a load of up to 400 tons. To make that possible a chamber was built that was 63 meters long and 8 meters wide.
But that, too, quickly ran at maximum capacity. The planning process for a second lock started in 1977. The idea was to add the new lock and keep the old lock running at the same time. All plans had to be taken back to the drawing board when the lock had to be closed in 1993 after it had become structurally unsafe.
It took two years to complete the planning stage for the new lock. During that time ships had to put up with a three-hour detour to cross from Lower Havel into Upper Havel.
The foundation stone for the new lock was laid in 1998 and by summer 2002 it was finally fully operational. The new chamber is 115 meters long and 12.5 meters wide. It lifts and lowers ships 1.80 meters to 2.40 meters, depending on the water level. Including entering and exiting, it takes about 30 minutes to pass the lock.