structure is layered, with an outer waterproofed casing of reinforced concrete 4 centimeters (2.5 inches) thick, and an inner concrete dome that is insulated by a layer of urethane foam. The projection dome was separate from the outer dome, and was 23 meters (75.4 ft) in diameter. Made of curved aluminum sheets, it was lap jointed to create a continuous spherical surface. The sheets were painted white and perforated with 2.5-millimeter (0.1 inch) holes, which were designed to let sound through and reduced echoes in the cavernous space. The building had two main entrances: a main entrance at ground level that faced east onto Queen's Park Drive, and a connecting passageway from the Royal Ontario Museum from what used to be the Mineralogy Gallery. On the wall opposite from the ticket booth and coat check was an evocative quote from Dante Alighieri Divine Comedy. Admission to either facility allowed visitors to see exhibits in both buildings, though a planetarium show cost extra. Zeiss-Jena planetarium projector The planetarium projector was the focal piece of equipment at the planetarium. It was a Universal Projection Planetarium type 23/6, made by Kombinat VEB Carl Zeiss in Jena, in what was then East Germany. The planetarium projector was a -long dumbbell-shaped object, with -diameter spheres attached at each end representing the night sky for the northern and southern hemispheres. Connecting the two spheres was a framework that held nearly 150 individual projectors, including those dedicated to the planets, the Sun, and specific stars. Improvements were made to the original planetarium projector over the years, allowing for special effects that could show close-up displays of specific planets, and the Sun and Moon projectors could replicate the experience of a solar or lunar eclipse. The projector could be controlled by a console where an individual presenter would provide specific talks or lectures. By the mid-1970s, automation features were added, which led to the creation of prerecorded shows. Most visitors to the facility would have seen an automated 40- to 45-minute audio/visual show on a particular space-related topic. Two types of shows were typically alternated on a daily basis: one aimed at families with young children and another aimed at older children and adults. Typical shows aimed at both audience types were built around themes such as space travel, the mythical stories behind the constellations, and around Christmas-time, a show that investigated theories on stellar explanations for the