"Arrow Cave is a pretty stupid name, though. I know Batman has a Bat Cave but that makes sense. Bats live in caves. Arrows don't live in caves. They're inanimate objects, they don't live at all. Why don't you call it, like, "The Quiver?"
The Arrowcave functioned as a base of operations for the super-hero known as Green Arrow and his partner, Speedy. Located beneath the old Queen estate in Star City, the immense cavern allowed the heroes the ability to hone their archery skills. It also provided shelter for the Arrowcar and Arrowplane. In recent years, the swamp monster known as Solomon Grundy had taken to using the cave as a private shelter. He has since abandoned the cave however following a fight with Green Arrow and Speedy.
The Arrowcave is common to the continuity of both the Earth-Two versions of Green Arrow and Speedy, as well as their Earth-One/Post-Crisis counterparts. The concept of the Arrowcave was based on designs (originally) envisioned by Batman and Robin.