The Iron Boots are a pair of metal heels that can be attached to Rouge's regular boots. Once equipped, they allow Rouge's attacks to destroy iron craters. Using this Level Up Item leaves a pink energy trail. They are the equivalent to Knuckles the Echidna's Hammer Gloves.
The Iron Boots are found in the Mad Space stage on the Spherical Planet. The actual location in the stage differs between the original Sonic Adventure 2 and Sonic Adventure 2: Battle:
Sonic Adventure 2
In Sonic Adventure 2, at the beginning the stage, head down the red-lighted launch pad and turn on the switch which will activate a rocket on the platform in front of it. It will then take you to the Capsule Planet. This is the only rocket that will take you away from the "start platform" as it will be the only one without an iron container covering the switch that activates its rocket. This also makes it impossible for you to take the rocket directly to the Spherical Planet, as its switch will be covered by another iron container.
Once you have taken the rocket to the Capsule Planet, you can Glide directly from the Capsule Planet to the Spherical Planet. On the top of the Spherical Planet you will find a metallic building where the Iron Boots can be found on the inside.
Sonic Adventure 2: Battle
In Sonic Adventure 2: Battle, the switch that will activate the rocket directly to the Spherical Planet will be the only switch without a iron container covering it, while the switch that activates the rocket to the Capsule Planet will be covered by a new iron container. As a result, when beginning the stage, head down the yellow-lighted launch pad and turn on the switch that will activate a rocket on the platform in front of it. It will then take you directly to the Spherical Planet. Proceed to the metallic building on top of the planet and the Iron Boots can be found inside of it.
In Sonic Adventure 2, the stage's layout allows this Level Up Item to be skipped. While this may make some emerald shards harder to obtain, it can be done. If an emerald shard were to be blocked in some way by an iron container, one could allow him/her self to die or fall off the stage and the emerald shard would relocate to another location.
While it is possible to skip this Level Up Item in the Dreamcast version, it is impossible to skip in the Gamecube version without cheating.
The Iron Boots share their name with an item in The Legend of Zelda series.