Mirror Hall

The Mirror Hall is a building in Super Paper Mario. It appears on the border of Flipside and Flopside. After Chapter 4, Outer Space, Mario will have to go to Flopside to open the door to Chapter 5 in Flipside Tower. However, to do that, he has to pass through the Mirror Hall, which (as aforementioned) is on the border of the two cities and therefore connects them.

Using Fleep, Mario will have to find a thunder mark in Flipside and flip it to reveal a secret passage. Mario must flip to 3D, enter, go to the door at the end, enter it and he'll find himself in Mirror Hall. Mirror Hall, when first approached, has four blocks and a mirror in the center.

Mario must hit the blocks in order from right to left until he has hit all of them. After that, the mirror will break. Mario must flip to 3D, enter the mirror and find himself in the Flopside section of the Mirror Hall. At the end of the Flopside part of Mirror Hall is a door going to the town of Flopside.

Passing the Mirror Hall is the only free way of getting from Flipsode to Flopside. However, the player can find Welderberg in two parts of Flipside; if they pay him 300 Coins, he will build a pair of arguably fast Warp Pipes between the interdimensional cities.

Trivia

 * It is interesting to note that, because the Mirror Hall is located between Flipside and Flopside, the direction it flips changes when Mario flips, depending on which side he entered the Mirror Hall from.