World 4-1 is the first level of World 4 in Super Mario Bros. This level introduces the Lakitu and Spiny enemies in the series.
The level starts with a pipe containing a Piranha Plant. Once the player jumps over the pipe, Lakitu will appear and begin throwing down Spinies, and will continue to do so throughout the level if Lakitu isn't defeated. Also next to the pipe are two ? Blocks, with the bottom one containing a power-up. Afterward is stretch of land with several coins and ? Blocks, and above the second to the right ? Block in the row of four is a Hidden Block containing a 1-Up Mushroom. After the row of blocks is a stone pillar followed by a couple of pipes, and another Lakitu will appear in this area is the previous one was defeated. Through the second Warp Pipe is an underground area with some coins and another power-up in the block above the exit pipe. After the entrance pipe is a row of blocks, with the third from the left also containing a power-up. After the exit pipe are some gaps and another stone pillar before the stone stairs leading to the Goal Pole, which has a Coin Block before it.