1989 Oldsmobile Tube Car

Early design work on what would become the Aurora began as early as the late 1980s and manifested itself with a 1989 engineering concept known as the Oldsmobile Tube Car. Beyond the overall similar shape, the Tube Car featured many detailed elements that were later found on the production automobile, including a full-width taillamp, wraparound rear windshield, and frameless windows. Unlike the eventual production car, the Tube Car was of a pillarless hardtop design with suicide doors.

Source: wiki

Images: GM