 The Manhattan Project was the successful effort by the U.S. government to develop an atomic bomb during World War II.Anaheim Hills and Irvine, California; and Mililani, Hawaii, began construction in the 1970s, but have not been completed due to their size, and will not be completed for at least ten years.Examples of unbuilt planned cities include Walt Disney's Progress City in Florida and Frank Lloyd Wright's Broadacre City.