The MAIN TOWER was the first high-rise with a fully-glazed façade to be built in Europe. The building thus stands out with an optical simplicity and transparency that conventional skyscrapers usually lack and that perfectly matches the MAIN TOWER's character as a publicly-accessible building.
In addition to aesthetic aspects, the extraordinary façade engineering has particular advantages in terms of light and ventilation. 2,550 exterior windows can be opened individually and thus supply fresh air whenever it is needed. At wind speeds above 70 km/h or temperatures below 5° C, the windows automatically close by themselves.
By the application of architectural bronze, the architects gave the square tower's grid facade an aesthetic independence which stands in formal contrast to the design of the round tower. In the base section, the listed exterior design of the predecessor building was integrated in order to create a visible contrast while at the same time achieving a harmonious connection between past and present.