the floor plan forms a triangle with slightly outwardly curved sides. the tower appears open and transparent due to the atrium, also triangular. a double-skin facade encloses the building. the stepped top of the tower creates a striking building termination and sets an expressive sign for the banking district. the building was constructed from 1994 to 1997 and cost 600 million dm. it has 56 floors and an area of 109,200 square metres. the architect who designed the building is norman foster. the skyscraper weighs about 200,000 tonnes and contains 18,800 tonnes of steel - twice as much as the eiffel tower in paris.