Tegel is a funny airport - quite minimalist for the capital of a major European power. In that respect, it it reminiscent of Bonn - a sleepy provincial town that used to be the the capital of the Federal Republic (prior to the unification.) Both Tegel and Bonn create an illusion of visiting Disneyland - where structures are scaled down to create a sense of gemuetlichkeit - yet they are fully functional real-life places, not hyper-reality theme parks created for entertainment.
Tegel is actually quite functional - my only complaint is the absence of rail connection to the city, which is rather unusual for Europe. However, its small size is bad for long distance travel. I once missed a Continental flight to Newark due to a late arrival of my connecting Lufthansa flight. It turned out that it was the only flight to the US from Tegel - as a courtesy, Continental offered me place on their next day flight without a surcharge (sic!) which I politely declined. Lufthansa, otoh, had plenty of transatlantic flights, but all of them from Frankfurt or Munich.
After the transfer of the capital to Berlin, Bonn reinvented itself as a "UN - city" to retain some of its previous stately splendor. The end result, however, is the retention of the Disneyland character of the city where the international rubs elbows with the provincial.
It is too bad that Tegel has to go to create room for a more modern airport. The new Berlin architecture is absolutely dreadful, just as most modern architecture in general and airport buildings in particular are. So in that respect, Tegel will share the fate of Penn Station in NYC, an interesting but not quite functional building replaced with architectural monstrosity in the name of efficiency. The French converted d'Orsay terminal into an art museum. The Germans could do something similar with Tegel. Do not raze it. Convert it to, say, a cultural center similar to the Smithsonian combining museums of transportation, natural history, art from all over the world, international cinematheque - in a word a place offering a virtually connection to the world in the way that the old airport never could.
