Known to Milwaukeeans as “The Domes,” this horticultural conservatory designed by Donald L. Grieb was completed in 1967. The complex conoidal structures consist of triangular, diamond, and hexagonal shaped sections welded together on a pre-cast concrete framework. An outer layer of glass and aluminum ensures maximum sunlight. The domes are 140 feet in diameter and 85 feet high. Widely differing climates are maintained in the Tropical Dome with an 85% relative humidity, and the Arid Dome with a 35% humidity, in which the flora of these areas flourish. Seasonal displays of flowers and trees take place in the Show Dome.

Mitchell Park was established in 1889, and the first horticultural conservatory there was built in 1898. More than 350,000 persons visited that site annually until it was razed in 1955. Mrs. Lyndon B. Johnson officially opened the new conservatory as part of her “Keep America Beautiful” campaign. In 2008, while undergoing repair or replacement of glass in the Domes, a special lighting system was installed to highlight the structures at night.