We are living in a new urban age, and its most tangible expression is the "supertall": megastructures that are dramatically bigger, higher and more ambitious than any in history.

Cities around the world are racing to build the first mile-high building, stretching the limits of engineering and design as never before.

In this fascinating work of urban history and design, TED resident Stefan Al-himself an experienced architect-explores the factors that have led to this worldwide boom. He reveals the marvellous and under-appreciated feats of engineering that make today's supertalls a reality, from double-decker elevators that silently move up to 50 miles per hour to the sophisticated blend of polymers and steel fibres that enables concrete to withstand 8,000 tons of pressure per square meter. Taking readers behind the scenes of the building and design of remarkable megastructures, both from the past (the Empire State Building, St. Paul's Cathedral, the Eiffel Tower) and the present (Dubai's Burj Khalifa, London's Shard, Shanghai Tower), Al demonstrates the impact of these innovations.

Yet while the supertall is undoubtedly a testament to great technological victories, it can come at an environmental and social cost. Focusing on four global cities-London, New York, Hong Kong and Singapore-Al examines the risks of wealth inequality, carbon emissions and contagion that stem from supertalls. And he uncovers the latest innovations in sustainable building, from skyscrapers made of wood to tree-covered buildings, that promise to yield a better urban future.

Featuring more than thirty architectural drawings, Supertall is both a fascinating exploration of our greatest accomplishments and a powerful argument for a more equitable way forward.