Just like the old DDR, that this tower was once part of, you will need your entry ticket to leave. Right by Alexanderplatz stands this symbol of East Berlin. 365 meters tall including the masts, with a rotating restaurant at about 206 meters and a panorama level at 203 meters. Two elevators go up and down the tower in 40 seconds.
The price is €11 and you may have to wait in line a bit. Worth it? I had to wait about thirty minutes in line, all in all, and I consider that a maximum. The view from 203 meters is nice, but with Berlin being a very flat city there's really not much to see except 360 degrees of flat cityscape stretching to the horizon.