New Super Mario Bros. U: Superstar Road-4 -- Hammerswing Caverns

Hammerswing Caverns are filled with ice, so navigating is a little challenging. Take the pipe into the caverns and trigger the large icicle to fall. The level is filled with several large hammers that rotate. These will serve as some of the platforms. Watch them so you don't fall off. There's a platform just under the second hammer. It has an Acorn Mushroom to make your life easier. There are some Koopas ahead on the ice. If you time it well, you can use a shell to get a 1-up. Drop down to a set of three hammers that connect to form a path. Over the gap over the second and third hammers of this set is a gap where you can just barely see some coins. Wall jump up for the coins and the first Star Coin. Keep going to the right and you'll see a hammer on a path. Once you land on it, it will move to the right, swinging all the while. There's a pipe nearby on the lower right. Time your activation of the P-Switch with the swinging of the hammer to reach the second Star Coin in the upper right, then return to the main level. There's a Green Ring ahead. Soon, you'll find the third Star Coin over a hammer near the pipe at the end. Either use the hammer or fly and boost to get it. There's a hammer in front of the flagpole to make it easier to reach. This opens up the path to a Mushroom House.