Earlier today, writer Brandon Sheffield shared some map sketches of unused levels for Sonic the Hedgehog 2. The sketches came courtesy of veteran game designer Hirokazu Yasuhara, who worked on Sega Genesis installments of the Sonic the Hedgehog series. Hooray! Game history!
Yasuhara's maps feature some areas that should be familiar to anyone who played Sonic 2 back in 1992. There's Casino Zone, Metropolis Zone, Oil Ocean Zone … and Green Hill Zone. No doubt "Green Hill Zone" was the placeholder name for what would become Emerald Hill Zone in the final release, but as one Twitter commenter pointed out, it looks like Sega was enamored with re-using Green Hill Zone as far back as Sonic's Genesis heyday.
Unsurprisingly, the maps reveal plans for levels and ideas that never came to be. There are intriguing "warp points" on a couple of the sketches (there are no warps in Sonic the Hedgehog 2 outside of a level select cheat), and there are a few Zones that may seem familiar for reasons you can't put your finger on: Namely, "Dust Hill Zone," "Woods Zone," and "Genocide City Zone."
Dust Hill Zone is a cut level that featured in early previews for Sonic 2. Woods / Wood Zone was similarly cut. Neither is especially remarkable; desert and forest levels appear in Sonic the Hedgehog 3, so we can assume the unused ideas for Dust Hill Zone and Wood Zone were summarily recycled.
"Genocide City Zone," on the other hand, has become stuff of legend. Originally conceived as a city-based level, it was never intended to be as bleak or as bloody as its name suggests. Supposedly, Sonic 2's developers just wanted a level name that "sounded dangerous," but were initially unaware that "genocide" is a loaded term in English.
In any case, Genocide City Zone (which was renamed "Cyber City" at one point before it was simply absorbed into Metropolis Zone) was never a real level of any kind. However, Sonic fans have created lots of stories, fanart, and fan games to make up for Genocide City Zone's lack of lore.
As you might expect, the fanworks are dark, haunted, and contain little in the way of sunny skies or picnics. One creepypasta relays a "haunted game" story about someone who found and played Genocide City Zone, only to discover the level is littered with the bodies of the little animal buddies Sonic usually saves at the end of each stage. There's even a fan-made "long version" of Sonic 2 that "restores" Genocide City Zone. There aren't any dead animals within, but it's still a grim place lit by forked lightning and a glaring urban moon.
Imagine if Genocide City had come to fruition, though. That would have added an interesting flavor to the SNES vs Genesis schoolyard wars of the '90s:
"Mario World has 'Chocolate Island?' Stupid babyish Nintendo! Sonic 2 is so cool. It has a Zone named after the systematic human-orchestrated massacre of ethnic groups and their cultures!"