The Fortress of Solitude is a fictional fortress appearing in American comic books published by DC Comics, commonly in association with Superman. A place of solace and occasional headquarters for Superman, the fortress is typically depicted as being in frozen tundra, away from civilization. Its predecessor, Superman's "Secret Citadel", first appeared in Superman #17, where it was said to be built into a mountain on the outskirts of Metropolis. By issue #58 (May–June 1949) it is referred to as the Fortress of Solitude, seems at a glance to be a freestanding castle, and is said to be located in a "polar waste". When the Fortress reappears in 1958 and for the first time takes center stage in a story ("The Super-Key to Fort Superman", Action Comics #241), it is again an underground complex in a mountainous cliffside. Traditionally, the Fortress of Solitude is located in the Arctic, though more recent versions of the Superman comics have placed the Fortress in other locations, including the Antarctic, the Andes, and the Amazon rainforest. The general public in Superman's world is either unaware or at best only vaguely aware of the existence of the Fortress, and its location is kept secret from all but Superman's closest friends and allies (such as Lois Lane and Batman). A trademark of the Fortress is that it contains a memorial statue of Jor-El and Lara, Superman's Kryptonian parents, holding a large globe of Krypton. Although Superman has living quarters at the Fortress, his main residence is still Clark Kent's apartment in Metropolis. The arctic Fortress of Solitude concept was first created for pulp hero Doc Savage during the 1930s.