The outer surface of the doubly-curved roof slab is covered by a total of 195 roof lights, varying in diameter from 1.50 m at the outer edge to 2.50 m at the highest point in the centre. These “eyes for art” were specially developed for the Städel extension and are designed to be walked on. Daylight entering the exhibition space Städel below can be controlled; either augmented using the integrated LED lighting system or mitigated by shading elements built into the roof light.