Detroit's Michigan Theater, built in 1926 by movie-palace makers Rapp & Rapp, as it looks today.
According to Wikipedia: "The Michigan Theater was permanently closed and partially demolished in 1976. Due to problems with the structural integrity of adjoining office building, the main hall and lobby were gutted and converted into a parking structure."
Photo from a new PBS documentary on Detroit (via NYT).
For more sad documentation of decline, see the documentary, Preserve me a Seat.