This is the Leipziger Tower. You can find the tower in the middle of the main street called Boulevard. In former times the tower was part of the city wall. Today there is not much left of the old city wall, you can see parts of it in Waisenhausring street.
In former times an important trade route went through Halle leading to Leipzig. This route passed this tower. Today you might imagine the route if you take a look at a map and follow Bundesstraße B6.