It's something that might trip people up, but due to West/East Germany split and Interflug going under after unification, Berlin airports are peripheral - leaves in flight graph, not hubs except for low cost airlines. Lufthansa continues to use Munich and Frankfurt as hubs.
A lot of airports are vast complexes and takes you a while to get from A - B, Tegel was quite quaint in comparison!
Admittedly for a major/global city - it was too small.