When the original Sonic the Hedgehog 2
released for the Sega Genesis way back in 1992, it contained an abandoned level called Hidden Palace Zone, which could only be accessed via a cheat cartridge.
All these years later, a pair of independent developers has resurrected the forgotten level as part of Sega's iOS and Android remastered release of Sonic 2
, with brand new enemies, obstacles, and a boss battle. It's available today on app stores.
It's the work of independent developers Simon Thomley and Christian Whitehead, founders of Sonic fan site Sonic Retro, and the people who made the other remastered iOS versions of old Sonic
This new version also allows players to rush through as Knuckles -- of course, this has been possible before, through connecting the original Sonic 2
game with Sonic and Knuckles
Image of Hidden Palace Zone via SonicRetro.org