THE BAT CAVE. BtVS Intertext/Allusion.

In "The Yoko Factor" (4020) as Xander, Willow, Buffy, and Giles engage in a nasty fight brought on by Spike's manipulations, Xander remarks (with Giles in mind):

Xander: Oh. Okay. You and Willow go do the superpower thing, I'll stay behind and putt around the Batcave with crusty old Alfred here.

In the Batman comic books, television series, and films.The Batcave was Batman's very high-tech sanctum sanctorum, located beneath Wayne Manor, from which the superhero and Robin the Boy Wonder venture forth to battle criminals of Gotham City.

--David Lavery