CCTV Headquarters, Beijing

Rem Koolhaas/OMA's CCTV Headquarters (2012) defied every convention of the skyscraper with a continuous loop form — two angled towers connected at top and bottom by horizontal overhangs. The overhang at the top cantilevers 75 metres, creating one of the most structurally daring buildings in the world. The building required the development of entirely new engineering software to calculate its forces.