Architect Jean Nouvel was inspired by the graphics and optical illusions of the Dutch artist M. C. Escher for the geometric cutting and positioning of the 340,000 bird silhouettes that adorn the facades, the forecourt and part of the roof of the Philharmonie de Paris. The birds come in seven shapes and four shades of grey. Those on the facades are made of aluminium, the others of concrete. Their matt tones change according to the light and contrast with the shiny stainless steel scales that are criss-crossed, concave, convex or almost flat.