- Not to be confused with the video game Sonic Lost World.
Lost World (ロストワールド Rosutowārudo?) is one of the action stages featured in Sonic Adventure, played as Sonic's ninth and Knuckles' fourth stage. It is located inside the Shrine of Knuckles's race in the heart of the Mystic Ruins.
The stage can only be accessed in one of two ways: through the main entrance during an earthquake (Sonic), or through a vent at the back of the temple which can be unlocked by 2 stone keys (Knuckles).
The level is an abandoned world consisting of temple passages with large water streams and inflamed traps, including protruding bars and rolling boulders. The level is divided into three main parts: a long maze-like section that ends with a flooded room where switches must be pushed to open the door, a dark passage with a waterfall and bolder running segment, and a room with panels that can be walked on when aligned. Sonic goes through all three, while Knuckles goes through only the third. Skill and timing is required to master this level.
To make traveling in water easier, there is a Snake-like rocked version which can travel on the surface and into water. Some parts of the interior, takes place in an Bottomless pit with some small platforms that cannot be seen without light. So to light them on, a system of light projectiles can produce some light in a part of these sections, which also includes mirrors that make the light reflected to light up the largest possible parts. There are also some puzzles to resolve in this part of the shrine.
There are five sections scattered across the stage. The first one has a large swimming snake, which must be used to find three switches to open a door of snakes. The second room is dark and mirrors can be used to light it up. The third area has a waterfall, which leads to a pond with stepping stones resting in the water, followed by having to escape from a giant burning boulder headed straight for the player (reminiscent of the opening scene of Indiana Jones and the Raiders of the Lost Ark). The fourth is a giant room, which must be slowly climbed up using the mystical Lit Panels that allow the character to walk on walls. To walk on the panels, the player must connect a group of them with a nearby switch and once they are lit, the character can walk on them. Knuckles plays only in this area, and his ability to climb and glide makes it much easier. The final short area has two small ponds with a stone mural of Perfect Chaos, destroying the ancient Knuckles clan. This also foreshadows what will happen in Super Sonic's story.
- Level C - Go to the center of the ruins!
- Level B - Collect 50 rings and destroy the capsule!
- Level A - Destroy the capsule within 4 minutes 30 seconds.
- Level C - Find the three Emeralds!
- Level B - Find the Emeralds without using any hintballs.
- Level A - Find the Emeralds within 1 minute.
Differences between the Dreamcast and GameCube
- The Dreamcast version has more foliage, some growing on the walls and ceiling. The grass is greener, too.
- The entrance to the next area changed from a square entrance to a rounded arch in the GameCube version.
- Most of the area's textures are slightly different.
- The walls of the rivulet are thicker in the GameCube version.
Entrance to Snake Room
- The fog color is changed from a somewhat-blinding white in the Dreamcast version to a more subdued dark gray.
- The textures are slightly different, especially on the central circular structure. It is slightly more colorful on the GameCube version.
- It cannot be seen here, but the Dreamcast version maps a ground texture to the bottomless pit, while the GameCube version uses a fog texture.
- There is a glitch in Knuckles' stage that will allow him to access Sonic's entire portion of the level. Ironically, the same music is playing as in Sonic's music is completely different. The same glitch also allows Knuckles to complete the stage where Sonic would. What the player has to do is punch one of the blocks before the fire comes out and Knuckles will glitch through.
- This is the only stage in Sonic Adventure that only two characters can access, as opposed to three in all other stages. Additionally, this is the only stage in the game that is exclusive to Sonic and Knuckles.
- Time can be saved in Sonic's A-rank mission by running backwards on the giant snake instead of waiting for it to complete its loop around the room. Also, if one were to memorize where the platforms are in the dark room, then the entire section with the mirrors can be skipped to save time. Interestingly, the DX version of the game brightens up this area, rendering the mirrors completely unnecessary.
- In Knuckles' version of this level, different music is played that isn't heard when Sonic goes through the same area. Sonic can hear this music in his stage's last room if the player doesn't move or in his extra missions.
- The stone mural of Perfect Chaos shows what the designers intended him to look like. It was not shown in Sonic Adventure because of the technological limits of the Dreamcast, but his true form was shown in Sonic Generations during his boss fight.
- In addition, the mural was stretched and mirrored in the final game.