This “Secret Citadel” was located in a mountain range outside of Metropolis. It first appeared in Superman #17 in 1942, and it didn’t make many appearances. In those days, Superman’s ...

Anthony and Joe Russo, famous for directing a number of Marvel blockbusters including the upcoming "Avengers: Doomsday" and "Avengers: Secret Wars" were recruited to help bring "Citadel together.