Underground is a stage in Tekken 4. The fight takes place in a room where many people cheer the fighters on. They are near some boxes, crates, and barrels. A small bit of the floor that is elevated on one side of the stage can barely be stepped on.
- The people cheering on and the boxes count as walls.
- If a fighter is knocking their opponent into the walls, this can cause a cheering person to fall to the ground. This can be repeated many times so that the stage is full of onlooker models that will clip through the characters and each other, and can be knocked around further.
- When the player hits one of the onlookers and KO the opponent, the replay doesn't show the onlooker getting hit.