World 8-Big Tanks
From the Super Mario Wiki
World 8-Tanks is the first of two tank levels in Dark Land, being followed by World 8-Super Tank, and is the first level of Dark Land overall, in Super Mario Bros. 3. It is the only level accessible after clearing Pipe Land and its own completion unlocks World 8-. It is entered automatically upon touching the icon on the map.
This is a horizontally autoscrolling level, though it is only the tanks that move; the player will not move with the screen if they are standing on the ground. The player starts at the forefront of a battalion of moving tanks. The tanks are lined with cannons that fire either cannonballs or Bob-ombs, some have Burners on the front, and others have Rocky Wrenches. There is also a cannon that fires Giant Cannonballs before the Warp Pipe at the end of the level, which leads to a chamber with a lone Boomerang Brother that will end the level upon being defeated.