The Burj Khalifa in Dubai is the world's tallest structure at 828 metres. At this height the real enemy of architecture is not gravity but wind; the building's structural system is designed from end to end to defeat the wind.

Designed by Adrian Smith of SOM, the building rests on a system called the "buttressed core." Its plan is Y-shaped: a hexagonal reinforced-concrete core at the centre is supported by three wings reaching outward. These three wings buttress one another, stabilising the core against torsion and bending from every direction — like a tripod with its legs splayed. This is how to keep a very tall tower relatively slender while making it rigid.

The second structural cleverness is in the shape of the mass. As the building rises, the wings step inward (setbacks) at intervals and the plan twists slightly in a spiral. The aim is not aesthetic but aerodynamic: a regular prism produces orderly vortices in the wind, and these vortices can sway the building dangerously. A continuously changing, twisting section keeps the wind from forming a regular vortex — the wind is "confused." The Burj Khalifa thus defines the principles of supertall structural engineering by combining the buttressed core with aerodynamic shaping.