DOTLAN EveMaps

"Hammerspace is the notional place that things come from when they are needed, and where they go back to when not. The term was fan coined as the place cartoon characters and anime/manga characters would store the overly-large hammers and assorted weaponry they had a propensity for hitting each other with, especially for comedic effect.

The actual location of hammerspace is very hard to determine." - Tv Tropes