After Burton, Sir Peter Chalmers Mitchell and John James Joass were appointed to design the Mappin Terraces. Completed in 1914, the Mappin Terraces imitates a mountain landscape to provide a naturalistic habitat for bears and other mountain wildlife. In 1933 the Round House, designed by Berthold Lubetkin's Tecton Architectural Group to house gorillas, was one of the first modernist style buildings to be built in Britain. The following year the Penguin Pool, also designed by Tecton, was opened; both now grade I listed. The Modernist dual concrete spiral ramps of the Penguin Pool have made it famous as a piece of modern architecture, but in 2004 the African penguins were moved out of the pool permanently due to it being an unnatural environment for them.