Zim's Base

Though Zim's base appears to be simply a misshapen green house, underneath the surface are countless research rooms, observatories, and much more Irken tech; first built using an Irken base construction device, the house is where Zim, GIR, and Minimoose reside, guarded by several surveillance garden gnomes on the front lawn, as part of the base's defense system (albeit a flawed one). Zim's underground base is where the alliance of heroes are first transported as the Hunt for the Chaos Emeralds begins—not knowing that a human named Dib had earlier been experimented on before Zim's abrupt departure, and subsequently imprisoned by the base's computer. After the alliance leaves, Doctor Eggman later infiltrates the base and frees Dib, coercing the boy into joining him.

Five years later, Zim transports everyone back to his base after the events taking place at the Nazca Lines, but ends up trapping everyone else except Sonic there (seeing as he no longer trusts anyone), after using the base's teleporters to arrive at his space station; the group is forced to stay behind, but manages to use the base's technology to aid Sonic in his efforts on Xevious, hacking into GAMP's system and deactivating everything he controls so that Sonic can defeat him. Supposedly, after the War on Xevious, Zim's computer has shut down the base, seeing as Zim no longer needs it (not for hunting down the Tallest in space, at least).