World 5-3 (New Super Mario Bros.)
From the Super Mario Wiki
This level is filled with slippery ice and many Snailicorns. The first Star Coin is located on the top of a block of ice about a third into the level. Soon, the area will divide into a high and low road. Mario should hit a block containing a Beanstalk to take the high road, or he can just keep going to take the low road. The low road contains more enemies in a smaller space, but contains the other Star Coins. Mario should slide and duck into the low road and destroy some blocks containing the second Star Coin. After getting past the Snailicorns, Mario should Wall Jump up a wall to get the last Star Coin. Soon after the final Star Coin is the flagpole.