Eggman Land is a location mentioned in the Sonic the Hedgehog comic series and its spin-offs published by IDW Publishing. It has been referred to as Dr. Eggman's "terrifying personal theme park" by Sonic.
At least one previous incarnation of Eggman Land has existed in the past, during which it would menace the world.
The Fate of Dr. Eggman
Dr. Eggman, while amnesiac and living in a village under the kindly personality of “Mr. Tinker”, told Sonic that he would like to show him the completed Eggman Land in case he came back, leading Sonic to question whether Eggman’s amnesia was genuine. Having heard Eggman mention Eggman Land as well, Shadow tried to destroy Eggman to keep Eggman Land from menacing the world again until Sonic intervened and got him to go about this peacefully. Shadow thus had Eggman show him his Eggman Land, which was an indoor amusement park he had made for children and named after a word he remembered, clearing him of all suspicions.
Battle For Angel Island
While singing for the children playing in his Eggman Land amusement park, Eggman received a visit from Rough the Skunk and Tumble the Skunk. The skunk brothers proceeded to kidnap Eggman, who cried out for help as he was being taken away. 
- Eggmanland is a location that first appeared in Sonic Unleashed as a playable stage. Eggman had already intended to build such a location at several points before Sonic Unleashed, such as in Sonic Adventure (where it was referred to as "Robotnikland" in the English version).