 Architect Cass Gilbert designs included a very high proportion of usable – and thus rentable – floor space, with a great deal of light and a flexible floor plan that could be subdivided for different tenants.Up-to-date fittings were installed to encourage a high-class of tenants, including the world's fastest elevators, safety features, and a swimming pool.Gilbert adopted the Beaux-Arts style, using accented terracotta and glass to emphasis vertical lines, elegantly echoing the structural frame underneath and incorporating 15th and 16th century Flamboyant Gothic-styled features.