Ventris's secret fortress located somewhere in the far reaches of the Milky Way Galaxy. It is where Ventris secretly dumps his kidnapped teenage girls and eats them for breakfast, lunch, and dinner.
Nobody knows the castle's exact location; the castle actually teleports to another random location within the Milky Way Galaxy every 10 minutes, making pinpointing its exact location nearly impossible. The warp devices used to teleport the Space Castle originated from now lost Space Dragon technology, with significant modifications and improvements. The dark lady herself installed these upgrades, made from unknown, forbidden technology she developed herself.
Only dietmango has successfully located and infiltrated Space Castle, a feat he's done repeatedly to rescue teenage girls from Ventris's grasp. The last time this happened, Ventris managed to find Mango and caught him by surprise, almost killing the throat slitter. The two have since developed a rivalry, but Mango always seems to get away whenever Ventris transforms into a dragon. Seems unfair.