World 6-6 (New Super Mario Bros.)
From the Super Mario Wiki, the Mario encyclopedia
This level is the only one in the entire game that contains Chain Chomps. First, the player must jump on the Spin Blocks, and fly through the air, avoiding the Chomps along the way. If the player goes as high as they can on the platforms and goes left, the player can collect a Star Coin located on a Chain Chomp's post. After the Star Coin, they must continue left and slide down, leading to an area with another Star Coin with blocks covering the way to it. The player must use the Spin Block, get above a stack of Blocks, and use the Drill Spin, which reveals a P Switch. Activating it allows the player access to the Star Coin, and a few bonus Coins. After the midway point, the player can enter a Red Ring, which only works if they slowly spins down to it. To get the final Star Coin, the player must first destroy any blocks that block the Spin Blocks. Then, with perfect timing, they must spin onto the Koopa Paratroopa directly below another P Switch. After pressing it, they must hit the next Koopa in sight and bounce off of it into a nearby Warp Pipe. Here, they must slide down and Wall Jump to the Star Coin. In the final area, the player can enter several green Warp Pipes, being blasted higher each time. Lastly, when the player reaches a set of four pipes, they can enter the third pipe to reach the top of the flagpole.