Board Thread:Closed Site Discussions/@comment-24369231-20140105190502/@comment-679780-20140106184624

I can imagine Underground Zone to be a series of ruins built inside various large caverns and connected with rather modern rail lines for excavation. Not for mining but archaeological research, the mine carts usually filled with rocks as the archaeologist uncover the ruins from the rock while also they had to deal with lava from South Island west Side Island's volcanic activity.

(I never really believe Sonic 2 took place on South Island because of reasons.)