Bear Grotto Construction, ca. 1964 ID: 6023 | This file appears in: Mid Century Exhibits at the Cleveland Zoo Technological advances in the fabrication of artificial rock and the shaping of concrete allowed for the construction of attractive, naturalistic exhibits during the 1960s. | Source: Images courtesy of the Cleveland Metroparks Zoo Download Original File SourceImages courtesy of the Cleveland Metroparks Zoo "Bear Grotto Construction, ca. 1964" appears in: Mid Century Exhibits at the Cleveland Zoo