From the Super Mario Wiki
The Battlerock Galaxy is a galaxy in the Wii game Super Mario Galaxy. The galaxy contains many floating metallic saucers and planet-sized rocks with Cannons. The Battlerock itself is a huge rock studded with cannons that fire at Mario, and the inside contains many technical contraptions. Many robots and Bob-ombs appear in the galaxy.
NOTE: Unless otherwise noted, all names are unofficial.
The starting point of the galaxy is a bunch of saucers near each other. In the first mission, Battlerock Barrage, there are five Blue Star Chips that Mario must collect to create Pull Stars to lead to a Launch Star, which takes the player to the Moving Saucer. There is a ? Coin that creates several coins here. In the second mission, Breaking into the Battlerock, there are barriers that must be destroyed by Bob-ombs that come out of the dispensers. One barrier contains a Launch Star that takes Mario to the Molecule Planet. In the third mission, Topmaniac and the Topman Tribe, Mario must ride some of these saucers to a Launch Star, which take him to the Metal Bowl Planet. However, these saucer groups are in different places on Battlerock in each mission.
To get this saucer to move, Mario must spin the bolt on top of it. It takes Mario through an area filled with cannons and some electrical barriers. Mario can collect a ? coin that makes Star Bits come out of two cannons. At the end of this section are the Big Saucers.
There are two huge saucers here, each with some barriers that can only be broken by Bullet Bills, which are fired near the second big saucer. The Power Star is contained inside one of these barriers. On the Seventh mission, Luigi is trapped under one of these barriers, which have some poles next to the barrier, making it harder for the Bullet Bills to break the barrier. When Luigi is rescued, Mario gets a Green Power Star.
This Planet is shaped like a molecule, and it has Chomps moving all around it. There are Bob-ombs here that destroy a barrier containing a Rainbow Star and a Luma. The Luma takes Mario to a spiky area, which has a Launch Star that goes to the Battlerock Planet. There is also a Hungry Luma that, when fed thirty Star Bits, creates a Launch Star to the Garbage Planet.
This Planet is a giant rock with metal inside. Inside, Mario must use a Bob-Omb to destroy the barrier to the cannon. The player should then enter the cannon and aim for the Luma to free it, which could take two or three times (one if the player is experienced). When the Luma is freed, Mario can access a Launch Star to the Blast Missile.
On this colorfully tiled missile, Mario has to bring a Bob-omb to the cannon on its tip, avoiding the electrical barriers. Then, the player must enter the cannon and aim carefully past the moving pieces of metal, so Mario can reach the Power Star. If the player misses, Mario falls back to the missile.
A planet filled with multiple piles of trash. Apparently, this planet is actually supposed to be the ammo depot for the Battlerock Galaxy, which a lone Gearmo inhabiting the planet grudgingly tells Mario after he lands here. If Mario successfully blows up all the trash on the planet with Bob-ombs within the allotted 30 seconds, the Gearmo rewards Mario with a Power Star. Mario does not lose a life if he fails to blow up the trash within the time limit.
Metal Bowl Planet
This planet is a bowl made out of metal. Here, Mario must Spin a Spiky Topman in to an electrical barrier, thereby breaking the barrier, and freeing a trapped Luma. The Luma creates a Launch Star to the Gravity Planet.
Mario should enter a pipe which takes him to an area where the gravity changes by Spinning some arrows. Mario has to go through a series of moving platforms before entering a pipe to the Barrier Chamber.
This place has a Sling Star, which takes Mario to an area with Spiky Topmen, which the player must Spin them both into a barrier, thus disabling the barrier itself and taking Mario to a Launch Star, which takes the Player to the Topmaniac's Saucer.
This saucer is where Topmaniac is fought. It is filled with electrical barriers all over it. There are also some Spiky Topmen and Topmini here. When Topmaniac is defeated, he gives up a Power Star.
Battlerock Galaxy appears in Mario & Sonic at the London 2012 Olympic Games as the location of the Dream Hurdles. The event takes place on a giant saucer and the actual planet is in the background. The location is also used for the rematch against Dry Bones. The galaxy theme is also remixed.
Names in other languages