World 1-5 (Super Mario Bros. 3)
From the Super Mario Wiki
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World 1-5 is the sixth level of Grass Land in Super Mario Bros. 3 and the sixth level in the game overall. The level takes place in the underground tunnels with pools of water. In the original NES version, the cave has a white and light blue pallet, though later remakes show it as more of a dirt cave.
The player begins the level by immediately sliding down a slope, defeating four Buzzy Beetles, and landing in a pool of water. Progressing, the player will find two hanging and grounded Warp Pipes throughout the level with Piranha Plants. After the first pipe, the cave splits into two paths leading either above ground or continuing through the cave. The path leading above ground has a hidden pink Note Block that will send the player to Coin Heaven, and the path continuing underground has a ? Block with a power-up in it. Both paths will lead to a hill the player has to jump over to reach another cave entrance with more pipes and Piranha Plants, with one at the end of the slope having a Venus Fire Trap in it in the NES version. Going up through the Warp Pipe at the end will take the player to the goal of the level.