CCTV Headquarters, Beijing

Rem Koolhaas/OMA's CCTV Headquarters, completed in 2012 in Beijing, is the world's most structurally daring skyscraper loop. Its two angled towers, 234 metres and 194 metres tall, are connected by 75-metre cantilevers at top and bottom, creating a continuous form that required custom engineering software to simulate forces. The building uses 120,000 tonnes of steel—a 60% weight saving compared to conventional skyscrapers of equivalent height—making it 35% lighter than the average tall office block. It outperforms #3's Supertrees in structural innovation, achieving a stiffness-to-weight ratio unmatched by any building over 40 storeys. Despite its radical geometry, the structure withstands seismic loads of 8.0 magnitude, a testament to its pioneering computational design.