Contractors are aiming for the stars with ever taller residential and office towers. Worldwide, there are now at least 18 buildings which measure more than half a kilometre high, with the Burj Khalifa in Dubai breaking all records with its incredible height of 828 metres. The sky is no longer the limit, and visionary architecture continues to require new construction methods and innovative materials. In the immersive and interactive temporary exhibition "XXHL, giga tours et méga ponts", which ran at the Cité des Sciences et de l’industrie in Paris until March 2021, we took a look behind the scenes of these radical giants.