Security was as important a concern as stature for this 541m-tall New York City landmark. The key to both is a massive, incredibly robust core, made of ultra-high-strength concrete clocking in at 14,000psi. “It’s much stronger than any rock you could find,” says Ahmad Rahimian, director of building structures at WSP. That allowed the walls to be thinner, maximizing lettable area and minimizing the weight of materials required. More than 50% of the carbon-intensive cement content was replaced with industrial by-products, and over 95% of the structural steel was recycled.

One of a crop of “super-skinny” pencil-thin towers lining Central Park, 432 Park rises 1,396ft from a footprint that is just one 15th of its height. As a residential building — currently the world’s tallest — its movement had to be controlled far more precisely than that of an office, where the occupants can be evacuated during high winds. WSP’s solution partly relies on two rigid tubes made from 14,000psi concrete. This resulted in a very pure structure with no interior columns, offering uninterrupted views in every direction.

In Herzog & de Meuron’s 57-storey “Jenga tower” in Lower Manhattan, no two floors are the same. The building is a staggered series of irregular boxes, with cantilevers ranging from 10ft to 25ft, and every floorplate had to be able to support itself. WSP used a very strong concrete structure — 12,000psi at the lower levels and 7,000psi further up — concealed to allow a completely glazed exterior with views from almost every angle. With no dividing shear walls in the apartments, residents can lay out their living spaces as they wish or combine apartments horizontally or vertically.