Battlerock

The Battlerock is the titular battlestation that is visited in Super Mario Galaxy's Battlerock Galaxy. It is 1.6 miles in diametre. Its name stems from how it is a battlestation like the Dreadnought from the Dreadnought Galaxy and the fact that it used to be an asteroid before it was modified. Unlike the Dreadnought, the Battlerock is immobile.

Cannon Fleet Path
Visited in Mission 1: Battlerock Barrage, this region is pockmarked with cannons. These cannons will deal decent damage to their target, but Mario can avoid them as he makes his way through since their angle never changes. However, there are electrical wires so Mario has to be careful as he moves. At the end are two giant saucers that hold the Power Star. In the Purple Comet mission, 100 purple coins are here and on route to the battlerock, and Mario only uses the Moving Saucer.

Break In Point
This location is a small location visited in Mission 2: Breaking Into The Battlerock. It has normal Gravity on the outside and outward gravity in the interior.

Ammunition Depot
This area can be visited in Mission Secret: Battlerock's Garbage Dump. Contrary to the name of its mission, it is an ammunition depot, specifically the Battlerock's. The planet's inhabitant is a Gearmo who is clearing the depot.

Gravity Corridor
This area is visited in Mission 3: Topmaniac and the Topman Tribe, as Mario makes his way to the saucer that Topmaniac pilots. Inside is irregular Gravity, forcing Mario to use the Gravity Arrows to make his way through.

Barrier Chamber
This is visited only in Mission 3: Topmaniac and the Topman Tribe, en route to the saucer that Topmaniac pilots. It has downward gravity. Mario has to cut off the Power Lines to break his way through and reach the Launch Star that sends the plumber on his way to the boss area.

Trivia

 * Just like the Dreadnought it is similar to, the Battlerock uses a more serious, battle-oriented version of the Space Fantasy theme.