Without debug, Sonic and Tails fall to their deaths, a la Genocide City Zone.
However unlike Genocide City, there are actually some objects in this zone, though they seem rather screwed up. This one actually turns Sonic upside down!
There are also rings, and some similarities with the Chemical Plant Zone layout.
With debug you can also place a swing, however this means nothing. This swing is the one which appears in Green Hill Zone and Marble Zone, and is simply a leftover.