World 4-4 (New Super Mario Bros.)
From the Super Mario Wiki
This level features a lot of Wigglers. Mario can complete the Red Ring by getting a boost from a Wiggler. The first Star Coin is found in a small cave near a Wiggler. Later, Mario needs to hit a block that contains a Beanstalk to climb up it and continue. If the player goes left and Wall Jumps off the wall, they will find the second Star Coin. The last Star Coin can be obtained by sliding on a wall next to it, then Wall Jumping to the small pipes. After going through the Yellow Pipe, Mario reaches the flagpole.
There is a secret area in this level, reached by using a Mini Mushroom to go down the second small Warp Pipe from the left where there are four together, with a Wiggler on top. This secret area has a Mega Mushroom, and a lot of pipes to smash, along with some coins to collect.