The Runde Saal with its conference hall and rooftop garden was built in the years 1933–36. The striking crystal chandelier and the parquet floor consisting of various woods are still preserved from this period. The wall paintings in the four alcoves, depicting the four seasons, are the work of the artist Erich Sperling. The walls are partially covered with antique glass. A special gem is the adjoining conservatory with terrace, which was renovated in 2014.