Dome

"These round rooms are called domes. We observe galaxies from domes such as these."

- Rosalina

The Domes are rooms in Super Mario Galaxy located on the Comet Observatory. These are where Mario can transport himself to other galaxies. After Mario collects Power Stars, more galaxies appear. Using a blue Luma which turns into a Pull Star, Mario can view galaxies and then, using a Launch Star, he can fly to them. The majority of the Domes have five galaxies, with the exception of the final one, the Garden, which only has four.

Trivia

 * Whenever a Bowser or Bowser Jr. level is shown in one of the domes, the revolving galaxy icon representing it will always be rotating around counterclockwise like the other galaxies, though at a noticeable angle, perhaps indicating that it is not supposed to be there, or wasn't there prior to the events of Super Mario Galaxy.
 * The background music in the Dome changes once the player unlocks and selects a Bowser galaxy for the first time. It will stay that way until the player completes the level.