I was walking down Stresemannstraße the other day when I saw a small section of a wall standing in the median . I knew it wasn't part of the Berlin Wall, both because of where it was located and how it looked. It turns out that this piece is a reconstructed section of the Berlin Customs Wall, built in the 18th century in order to regulate trade coming into and out of the city. It allowed the city authorities to implement an excise tax on goods entering and leaving Berlin.
The wall was constructed beginning in 1734 by Friedrich Wilhelm I. This was NOT Frederick the Great. The wall replaced and expanded the old medieval wall, giving authorities control over a larger area.
The coolest thing about this wall is that its construction led to the creation of several city gates, including the Brandenburg Gate. While the Brandenburg Gate that we know and love was not built for a few more decades, the gate to Brandenburg was first constructed as part of the Berlin Customs Wall.
As the city expanded over the second half of the 18th century and first half of the 19th century, the wall became less necessary. It was demolished in 1867-1868.
The above-ground part of the wall is actually a reconstruction from the 1980s. The original foundation was excavated around that time, and can be seen in this photo. I assume that the garbage is vintage 1734 as well.