The functionally appropriate location of a building accommodating central facilities of the post office is in close proximity to the station. This applies specially to letter post offices, for a large part of the letters are handled by rail. Here, in the very heart of Cologne's old city the advantage of the location produced a planning problem. The densely built-up old city situation thwarted any extensions of the service building, forced parking for motorcars and heavy goods vehicles underground and necessitated a compression of the building volume to a considerable depth in order to reduce the building height to respond sensitively to the height and appearance of the surrounding historical edifices.