NBC's Air Castles: In 1947, NBC published this 54-page brochure which describes the company's production facilities in 7 different locations most of which had been given the name "Radio City" (as in Radio City Denver). NBC's Cleveland, Ohio facilities however, apparently were not given the Radio City name. The brochure appears to have been created as a gift to advertisers or members of the broadcast industry but not distributed to the general public. Copies are quite rare.