Each room generally contains a locked door and multiple enemies, one of which contains the key to the door. How does it work? As the name suggests, you'll have to work your way through 100 rooms to reach the goal.

Jump on it to open the way to the Pit of 100 Trials. When you reach the silhouette of the door, flip to 3D and run down the hallway that appears to find a Blue Switch. Point the Wii Remote at the screen to find a series of hidden blocks - click on each one to make it visible, then use them to cross the gap. Now it may appear there's no where to go from here, but looks can be deceiving.

Travel to the far wall and leap onto the top block.