Congo Jungle (コンゴジャングル, Kongojanguru) is a stage in Super Smash Bros. that reappears in Super Smash Bros. Melee. It is one of Donkey Kong's home stages. It is based on various levels from Donkey Kong Country, with pre-rendered backgrounds, environmental themes and tracks, and most notable in a battle, use of a Barrel Cannon for transportation (usually for a vertical recovery).
This stage comes from Donkey Kong Country. In Donkey Kong Country there is a level called Blackout Basement. In Blackout Basement there are two platforms that oscillate up and down. Later in the game is a level called Platform Perils which has platforms with arrows on them that move when the player jumps on them and they move in the direction that the arrow is pointing. In this stage there are two platforms that go in a circle which could be a reference to either Blackout Basement or Platform Perils. Also from Donkey Kong Country are barrels that the player could get shot out of. Certain barrels can move up and down, left and right, or move diagonally. There were also barrels that remained stationary, but they rotated around. In Donkey Kong Country 2 there are arrow barrels that fire at whatever direction it is pointing. In this stage there is an arrow barrel, but the barrel also moves side to side and can rotate. In the background near the sunset, a flock of Neckies can sometimes be seen flying across the horizon. In Donkey Kong Country, Neckies were among the most common enemies 
It is interesting to note that the name of the stage is incorrect, as the actual location in Donkey Kong Country is called "Kongo Jungle", with a "K". Congo, on the other hand, is the name of two countries in Africa, and a river that runs through them. In Melee, this was fixed. The music track that plays on this stage is from Donkey Kong Country's Jungle levels. 
This stage appears as a starter stage in Super Smash Bros. This stage is made up of a big platform with four small platforms above it. Two small stationary platforms are above the left and right sections of the stage, and between them are two smaller platforms that circulate clockwise. The main platform can be passed through from below, but not from above. Under the stage there is a Barrel Cannon that can greatly aid many characters' recovery. A player that gets into the barrel can exit either by pressing a button or waiting for a certain period of time. In either case, they will be shot in the direction that the arrow on the barrel is currently pointing. There can only be one character at the time in the barrel.
Congo Jungle is also known as Past Stages: Kongo Jungle in Super Smash Bros. Melee and is one of the three past stages that can be unlocked. To unlock this stage, the player must beat 15-minute Melee. The stage itself is a near-exact copy of the SSB version, only being slightly larger. There also seems to be a short delay when the player is launched from the barrel, which can almost always spell doom for the mis-aimed character in many cases.
 Tournament legality
This stage is a legal stage in SSB and is one of three starters (along with Hyrule Castle and Dream Land.) It is, however, by far the least common neutral played. Due to the stage's darkness, certain palette swaps are usually banned from play. Contrastly, the stage is fully banned in the Japanese ruleset, and unlike all other stage bans for the game, no definite reason has been given as to why.
The stage, however, was deemed at first to be a counterpick in Melee; although it had a relatively non-obtrusive stage design, it had a large size, which gave an advantage to faster characters and characters with projectiles, and a high ceiling, giving a slightly larger reliance on horizontal finishers. It was later banned in singles due to these traits, which were deemed unsuitable for two-player fighting. It still remains a counterpick in doubles, but it is seldom picked in tournaments.
 Description from the Instruction Booklet
The moving barrel beneath the stage could be your salvation if you get knocked off.