25m is the first level of the Donkey Kong arcade game and Donkey Kong on the Game Boy. It is the bottom level of the Construction Site in the latter game. The level starts with Donkey Kong capturing Pauline, Mario's girlfriend. The player takes control of Mario as he jumps over barrels and climbs to the top of 25m, where Donkey Kong and Pauline are located, via a series of ladders. Mario also finds hammers around the area, which he uses to smash the barrels. After reaching the top of 25m, Donkey Kong grabs Pauline and climbs up to 50m. The bottom of the level also features an Oil Drum. If a blue barrel enters the oil drum, it creates a Fire that tries to hunt down Mario. If there are five Fires simultaneously onscreen, Donkey Kong stops throwing blue barrels, and any remaining blue barrels do not create a Fire unless Mario thins their number.
In the original arcade, the slightly sloping nature of the iron supports as well as some of the broken ladders was explained to have been caused by Donkey Kong, shortly after reaching the top of the structure, jumping to the other side, the force of his jumps also bending the structures and tearing the ladders by consequence. It was cut, along with most of the cutscenes as well as one of the levels, in the NES versions due to space issues, but was eventually restored in the Game Boy version.
In the Game Boy version, two layers of platforms are removed due to the screen size restriction of the console. However, a level that has the exact appearance of the original 25m, albeit with a scrolling screen, appears much later in the game as stage 9-5 in the Tower.