The Buhl Planetarium has the oldest operating major planetarium projector in the world. The Zeiss Optical Works in Jena, Germany, manufactured the projector at a cost of $135,000. It has 106 lenses capable of producing 9000 images of stars. It was the first building of its type to have an operating theatre with a special sound system for the hearing-impaired. Architects Ingham & Boyd designed the building in 1939 in the stripped Classical style at a cost of $1.07 million. The octagonal dome is composed of copper and formerly hosted the most popular feature of the Planetarium, the sky show projected on the dome’s interior. The building boasts sculpted reliefs and Indiana limestone walls designed by Sidney Waugh, a well-known sculptor. The structure was the first public building in the City of Pittsburgh to be built with air conditioning.