This elliptical staircase made of cast concrete plunges into the depths of the basement of the Unterlinden Museum. It provides access to the underground gallery that connects both old and new wings of the Colmar museum. Designed by the Swiss architects Jacques Herzog and Pierre de Meuron, its design is inspired by the spiral staircases of the Middle Ages and the Renaissance. The virtuosity of its geometric design and the plasticity of its upward movement make it a technical feat. Built in the workshop, the casing was then dismantled and reassembled on site. The light is cleverly diffused to enhance soft indirect lighting.