Angel Island in DA FUTURE! Unlike most places on Mobius, it is not under Neo Metal Sonic's control, but is instead a haven for those who want to be protected from him...if you can call it that. The evil Dr. Finitevus brainwashed Knuckles into becoming the Master Emerald-powered Enerjak once more, and even though Enerjak claims Angel Island is safe, he puts any who come to it under his control. Of course, all of this is a secret, and more and more people come every day...
OOC: If names like "Dr. Finitevus" and "Enerjak" are unfamiliar to you, just go to Wikipedia.