25m is the first level of Donkey Kong and by far the most famous stage. It is also the simplest stage, with the goal being to climb up the girders to the top, where Donkey Kong is holding Pauline.
The stage's layout is fairly simple. It's a bunch of girders arranged so that the player can reach Donkey Kong without using ladders. The player does have to dodge the barrels Donkey Kong throws. There is also a hammer halfway through the stage. Barrels that hit the oil drum turn into Podoboos.