The Bat Cave!

 

 

The Batcave underwent a gradual evolution.  In the beginning, it was just a secret underground garage where Batman stored his equipment.

The producers of the 1943 movie serial decided it would be more spectacular if there were bats flying around in it though and christened it the Bat's Cave (Episode 2, July 1943).  This was shortened to the Bat Cave in an October 1943 daily comic strip. (art by Bob Kane and Charles Paris)

  

Batman 12, Sept 1942. (art by Jerry Robinson and George Roussos). The first time the name Bat Cave appeared in the comic was this story from Detective 83 from January 1944. (art by Jack Burnley).  Batman's trophy room also evolved over time

 
 
The spectacular trophies that became its centerpiece first appeared in Batman 48 (art by Jim Mooney) Aug 1948.  However, those trophies first had to appear in individual stories before they could be added to the Batcave collection. The giant robot dinosaur first appeared in Batman 35 (Art by Bob Kane and Ray Burnley) June 1946.
The giant penny first appeared in World's Finest 30.  Art by Bob Kane and Ray Burnley, September 1947.  The giant Joker mask proved to be the Harlequin of Hate's undoing in Batman 53- "A Hairpin, a Hacksaw, a Hoe and a Hole in the Ground" by Bill Finger and Lew Sayer Schwartz and Charles Paris.  I'm still not sure about the Joker Jack-In-the Box.