Few cities share tumultuous histories like Berlin does. One excellent way to discover how ordinary people coped with the division and the wall is with the Berlin Undrground tours organization.
Greg and I chose your M which introduced us to some of the successful tunneling projects that allowed Eastern Germans in small (8 to 15) groups to escape. Most tunnels were dug by student organizations from the West under the no-mans-land (se below watchtower and shooting zone) to cellars in the east.
Others yet got out on the subway which crossed the Eastern sector through ghost stations. It was absolutely fascinating to see the lengths to which people went to escape and how the Stasi police reacted with new measures to thwart copycats.
We ended our fantastic experience with drinks at night on top of the TV tower at Alexanderplatz. Built as the symbol of Eastern German ingenuity, this massive 368 meter tall concrete structure features a platform restaurant that turns at 1 rotation per hour as well as a viewing platform and a Bar.
It is a must see even if the weather is not perfect or it gets dark early (430pm in winter). Cheers!