City Beneath the Sea is a 1971 adventure science fiction television film and television pilot for a proposed series by Irwin Allen starring Stuart Whitman and Robert Colbert. It started as a conceptual 10-minute demo reel as a means to sell the plot and concept to television studios. The concept was not bought initially and a few years later Allen produced a two-hour telefilm for NBC. The two-hour movie again failed to gain the response necessary to be picked up as a series, but has remained a cult favorite amongst sci-fi and Irwin Allen fans. In the UK it was shown theatrically in 1972 as One Hour to Doomsday.