25m

25m is the first level of the Donkey Kong arcade game and Donkey Kong on the Game Boy. The level starts with Donkey Kong capturing Pauline, the girlfriend of Mario. 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 with. After reaching the top of the 25m, Donkey Kong grabs Pauline and climbs up to 50m. The bottom of the level also features an Oil Drum from which Fires emerge that try to defeat Mario.

In the Game Boy version, there have been two layers of platforms removed due to the screen size restriction of the Game Boy. However, a level that has the exact appearance of the original 25m, with a scrolling screen, appears much later in the game as stage 9-5 in the Tower.