The Ehrenfest house and its history: where bright minds met in an informal atmosphere and exchanged their many remarkable thoughts to the greater glory of science and Leiden University. The Ehrenfest house is located at Witte Rozenstraat 57 in Leiden. In his attic room here, Leiden Professor of Physics Paul Ehrenfest hosted physicists including Niels Bohr and Albert Einstein - who was made special professor at the university in 1920.