Crystal Palace
The crystal Palace is where the last Star Spirit is being held in Paper Mario. This palace is a 'mirror' filled castle with puzzles in every which way. Mario and his teammates must solve the puzzles and fight off many Duplighosts and White Clubbas to get to the boss. After solving the puzzles, they manage to reach the boss: the Crystal King. After they defeat him, they free the last Star Spirit, Kalmar.
Many of the walls look like mirrors, but they're actually just glass, because the reflections are always Duplighosts in diguise. The palace has two areas, the front (main) area and the rooms behind the glass walls. Each will need to be inspected carefully, because going back and forth between them can be confusing, since they're almost exactly the same.
The Crystal Palace was once a shrine to the Star Spirits, but it's location and how to get there became lost over time. The only way to reach it is a secret passage in Shiver Snowfield to Shiver Mountain, where at the top is the palace.
