DOWNEY — The building that housed the world’s first Taco Bell is under “imminent threat of demolition,” according to the Downey Conservancy, a Downey-based preservation group. Although Downey is more famously recognized as the site of the oldest operating location for the world’s largest hamburger chain, it is Taco Bell that built its very first location within the city. The building, located at 7112 Firestone Blvd, was opened by founder Glen Bell in March 1962.