fortress of solitude
Superman's first secret headquarters was his Secret Citadel or Mountain Retreat, which appeared in Superman 17
by Jerry Siegel and John Sikela in July 1942, beating out the Batcave by three months.  The Citadel appeared a couple of more times in the pre-war era and then vanished.
The name Fortress of Solitude was first used in Supeman 58 in May 1949, lifted from Doc Savage, who presumably didn't need it anymore.  The original Wayne Boring drawn Fortress looks like the world's largest Swiss villa.  And the inside is even more oppulent.  This was its only appearance.
The real Fortress as depicted throughout the Sixties and beyond, didn't appear until Action 241 in June 1958 in a story by Jerry Coleman and Wayne Boring.