World 9-4 (New Super Mario Bros. Wii)
From the Super Mario Wiki
World 9-4 is the fourth level of World 9 in New Super Mario Bros. Wii. This level involves a desert landscape, which has many pipes and auto-scrolls. Like all levels in World 9, there is no midway point. Most of its enemies are Venus Fire Traps and Bob-ombs. Its main power-up is an Ice Flower, which is required to get the last Star Coin.
This level is an auto-scrolling level that takes place in a desert containing many pipes. At the beginning, Mario must progress through various pipes while Venus Fire Traps and Bob-ombs attempt to stop him. Towards the middle of the level, Mario encounters Switchbacks, which are sensitive to weight. If two entities or more are on the platform, it starts to sink. At the end, Mario finds a pipe that leads him to the flagpole.