Hidden Palace Zone (Sonic the Hedgehog 2)


 * For the level from Sonic & Knuckles, see Hidden Palace Zone.

Hidden Palace Zone is a mysterious zone which was originally removed late in the development of Sonic the Hedgehog 2 for the Sega Mega Drive/Genesis. A similar stage with the same name later appeared officially in the game Sonic & Knuckles, serving as its inspiration. It is the most famous out of the scrapped areas not only because its intended music track remains in the Sound Test of the final version of the game (listed as number 10), but also because of its elusive exposure in magazines. It was among the last levels deleted from the game, as its icon is also in the game data (which is shown in the standalone Sonic the Hedgehog 3 Sound Test) and players can still access a garbled version of it with a cheat device.

Eventually, this version of Hidden Palace Zone was officially completed and included in Christian Whitehead's remastered edition of Sonic the Hedgehog 2 for iOS and Android devices.

Description
It is an underground cavern full of water featuring sparkling gems and rocky regal structures, possibly ruins of some ancient civilization. In the "Simon Wai prototype", there is a glowing bridge that is actually the same object as the bridge in Emerald Hill Zone but it checks the level number to make it glow. The idea of a bridge that will glow when Sonic runs on it was reused in Sonic the Hedgehog 3's IceCap Zone. There is also a large ramp in the cannot that cannot be climbed up without Debug Mode, and there are pipes similar to the ones in Chemical Plant Zone. A second act can also be accessed, but it is almost identical to the first without items, and is nearly empty.

In the 2013 mobile re-release, the zone begins with the player character falling through a vertical tunnel similar to the intro of Lava Reef Zone, as the finished Hidden Palace is now relocated under the second act of Mystic Cave Zone and as such, it only has one act. In addition to some familiar features, there are objects not previously seen in any version of the game, such as a jellyfish-type Badnik that acts similar to Grabber and a unique Robotnik boss fight involving musical instruments, explosive debris and water. When the Capsule is opened and the zone is cleared, the player proceeds to Oil Ocean Zone, skipping the remainder of Mystic Cave. In both the playable prototype and mobile versions of the zone, the track played is the 2-Player version of Mystic Cave, which is also heard in the game's credits; if it is accessed with a cheat device in other released versions, Track #10 from the Sound Test plays.

Development Info
An interview with Yuji Naka later revealed that Hidden Palace Zone was originally intended to be a level where the player would be warped to after collecting the 7 Chaos Emeralds. Once there, they would receive the power to transform into Super Sonic. The idea was scrapped and the ability was given to the player immediately. In ICEknight's interview with Craig Stitt he mentioned that it started as two acts but then switched to a single act before being cancelled.

Many parts of the level were once grounds for debate, such as the so called "Master Emerald" which blocks a speed pipe in the prototype and a spring in the mobile version. In actuality, this was meant to be just a breakable object similar to the ones found in Hill Top Zone. There was speculation about the level being tied to Tails somehow, due to the Tails 1-up monitor in this level. There have been other theories about the level, but most of them have been generally accepted as false.

Magazine Preview
A picture of Hidden Palace Zone, was sent to various magazines to promote Sonic the Hedgehog 2. It was determined not to be a screenshot from a prototype for several reasons: Sonic's sprite is different than any of those seen in a Sonic 2 prototype, Sonic is off-centered, he's running in mid air, the use of a different background, the placement of two enemies at the bottom, the non-italicized HUD, etc. These are some of the same characteristics seen in other promotional mock-up pictures sent out by Sega during the same timeframe.

Misplaced Monitors
There was much speculation about the Tails 1-up monitor until the truth behind it was uncovered. The monitor designations were reassigned and the object subtype number for the Tails 1-up monitor was originally the object subtype number for Sonic 1-up monitor in the first Sonic the Hedgehog. The early Nick Arcade demo, which was an early prototype of Sonic the Hedgehog 2 shown to be an edited Sonic 1, places Tails 1-up monitors in Green Hill Zone where the shield monitor should be. This proves that the Tails 1-up monitor in Hidden Palace Zone was meant to be a shield monitor instead of a Tails monitor. The Tails 1-up monitor must have been placed early in the game's development cycle (before the programming for the object subtypes was changed) as it was one of the first levels to be worked on as the Nick Arcade prototype shows. Had the level originally been worked on further, it's certain the Tails 1-up monitor would have been swapped with the proper Sonic 1-up monitor. Among the major changes made to the level layout in the remastered mobile release, the monitor is absent and replaced with a shortcut just beyond the space it occupied.

The shield monitor in the beginning was also presumably meant to be a Super Ring monitor, based on the changes in object subtype numbers.

Trivia

 * Track #10, believed to have been the finalized BGM of Hidden Palace before the zone was originally cut, was not used in the 2013 re-release of Sonic the Hedgehog 2 because developers did not think it fit the pace or prehistoric feel of the level. It should be noted, however, that Track #10 was labelled "Unused Song" in the Sonic the Hedgehog 1&2 Soundtrack released in 2011, and Masa's Demo Version included a definite end to the track rather than the in-game loop, suggesting that the music may have instead been intended for the deleted cutscene in which Super Sonic is unlocked rather than the actual level theme.
 * In any released version of Sonic the Hedgehog 2, finishing the level (which requires hacking in most versions) will take the player to Oil Ocean Zone. This excludes the Nick Arcade prototype - since Oil Ocean does not exist at that point of development, the game will redirect to a garbled version of Labyrinth Zone (as the Nick Arcade prototype is based off the original Sonic the Hedgehog).