The architect was not Speer, but one Ernst Sagebiel. Sagebiel had run the office of one of the great pioneering modernists, Erich Mendelsohn (1887-1953), who was based in Berlin until the advent of the Nazis in 1933, whereupon he moved first to Britain, then Palestine, and finally in 1941 to the United States. But as early as 1914, Mendelsohn had speculatively designed what he called an aerodrome. He envisaged a huge building, 1300 to 1500 feet long. He imagined a curving plan, with a tall central hall to handle six airships, and low hangars for aeroplanes and workshops to either side. He was never commissioned to build an airport.

But his ex-employee Sagebiel was. Clearly he was a fine architect, and when he had to adopt the classical mode favoured by his new masters, he did so in an austere manner reminiscent of the earlier work of Sweden's Gunnar Asplund. Tempelhof's tall hooded stone window surrounds were later spotted by the architect James Stirling, an Asplund enthusiast, who copied them on his Berlin Science Centre (Wissenschaftszentrum) in the mid 1980s. But for all that, Tempelhof is Mendelsohn's Expressionist/Futurist 1914 aerodrome design in disguise. The tall central hall is there, only for people rather than airships. The curving wings with their configuration of hangars and workshops are there. Its proportions are different, and the style is wholly different, but Sagebiel had learned well from his old boss. Do not be fooled by the surface appearance: this is a very modern, efficient building, just as the Gothic fantasy of Sir George Gilbert Scott's St. Pancras Station in London (1868-74) conceals an ideal plan for a rail terminus.

It did not surprise me to learn that the architect Sir Norman Foster, who flies his own planes, considers Tempelhof to be one of the world's great airports. It is said in his office that it was a big influence on Foster's own first airport, Stansted. Not in its surface styling, of course - Foster is not yet so conservative as that - but in its plan, which is near-perfect. You arrive at the front, you traverse the departures hall, and you walk out the back onto your plane, which is drawn up under that huge canopy. Nothing could be simpler or more direct. No travelators, no piers, no being extruded along tubes, no miles to walk. The bulk of the complex's office space forms the colossally grand approach. The hangars curve a very long way round on either side, embracing the oval airfield. But the main activity - arrival, process, departure - is kept within that tight, perfect central diagram.