Finlandia Hall features an optical illusion: the National Museum building on the other side of the street seems to rise from the edge of the Finlandia Hall tower. The effect is created by a black trapezium on the white marble surface of the Finlandia Hall tower. The trapezium has been measured to fit the rising tower of the National Museum when the Finlandia Hall is viewed from the eastern shore of the Töölönlahti Bay. Aalto liked to create optical illusions. Another example of this can be found on the pedestrian path behind the library building of the Helsinki University of Technology (current Aalto University) in Espoo.