Historically, architectural principles included the need to make a building look stable, safe and secure. While modern materials have progressively challenged this notion, nowhere has it been more flouted than in the Gate of Europe towers in Madrid, Spain. To overcome practical difficulties (the footprint of these buildings needed to clear the subway interchange at street level), the designers created twin towers that lean in at an angle of nearly 15 degrees.
In order to provide pedestrians and occupants with the required sense of safety, structural steel members are clearly expressed on the building exterior: most notably, each tower has an uninterrupted vertical beam on its north and south elevations. Concrete cores and underground counterweights further stabilize the structures.