The Kongresshalle is the largest Nazi monument building (1935-40) to have been preserved. It was built based on the Colosseum in Rome. The U-shaped building is 39 metres tall, measuring 240 x 200 metres on the outside and 175 x 155 metres on the inside. The open-air inner circle is partially tarred; the building is made from unplastered brick; partially clad with granite panels. The round building features long walkways, colonnades and large windows. The building is partially tenanted and partially used as a museum (Nazi Party Rally Grounds Documentation Centre).