Retro World
The Retro World, commonly nicknamed the Floing Void, is a rift in time and space. It makes up Chapter 7 of Mysteries of Fire Island, according to the official solutions page.
While it looks remarkably like the Void, there are some differences. First, there is no music. Second, the pillars emit small red star particles. Finally, the Stinkers that travel to the Retro World (Guggenheimer and the player) note that it somehow feels different than the void, saying without a doubt that it is something else.
Guggenheimer feels the presence of Floing magic strongly in the region, and urges the player to use a Floing orb on a nearby pillar. Upon doing so, an Adventure Star appears, leading to the first Wonderland level ever: First Steps. The player realizes that this may only be the beginning of the adventures in the Retro World, and looks forward to more.
There are ten adventures in the Retro World. Upon completion of "First Steps, Revisited", a bridge leading to four more pillars activates. After all those are completed, a bridge opens leading to four more pillars (these ones leading only to Classic Trilogy-style Adventures, not actual remakes). Once all those are completed, the final pillar is reachable: a level entitled "Remembering Shorty", a memorial to Wonderland Community Board member Shorty who passed away due to illness.