World 1-2 (Super Mario Bros.)

World 1-2 is the second course of World 1 in Super Mario Bros.. It is the first underground level, and it holds the infamous Warp Zone, which, if done correctly, the player can use to enter Minus World.

Layout
The player starts the level by falling through a hole in the roof by a pipe. There will be two Goombas and five Question Blocks. The first one contains a Super Mushroom or Fire Flower, the other four ones contain coins. There will be a block tower structure, where there's a Goomba and a Brick Block with 10 coins. Ahead, there will be some Brick Blocks, one of them containing a Star and some Coins, with two Koopa Troopas underneath them. The player will reach a place filled with Brick Blocks with a Koopa Troopa and five Goombas. There will also be a Brick Block with a Super Mushroom or Fire Flower and a masked Brick Block with ten Coins. There will be a Pit and, after it, a Block platform that allows Mario to get an 1-Up Mushroom. The player will find two Goombas and three pipes, all of them containing Piranha Plants. The player can enter in the first Pipe, that will lead them to a room with Coins and a 10-Coin Brick Block. The player can exit the area by a Warp Pipe in the extreme right. This pipe will lead to the third one in the main area. There will be two gaps and, between them, two ground blocks and some Brick Blocks. After that, a small, half-pyramid structure with two Goombas is seen. Ahead, a group of platforms will be rising and falling. Between them, a Koopa Troopa and some Brick Blocks. The player will reach a Pipe that will lead them to the final area. They can use the platforms to reach a Warp Zone hidden through the roof. From right to left, the first pipe will head to World 2, the second one will lead to World 3, and the third one will lead to World 4. If the player goes through the regular level pipe, they will lead the player to a pipe with a Piranha Plant in an overworld area. There will be a Block half-pyramid that allows the player to jump on the top of the Flagpole.

Enemies

 * Goombas
 * Koopa Troopas
 * Piranha Plants

Trivia

 * This level has also been recreated in various games, including Super Mario Advance 4: Super Mario Bros. 3 (as a World-e level), New Super Mario Bros. 2 (within the first course of the Gold Classics Pack), Super Paper Mario (as part of Chapter 3-1), and Super Smash Bros. Brawl (as an alternate version of Mushroomy Kingdom; there is a chance this stage will be played instead of World 1-1).
 * Mario Kart 8's Super Bell Subway heavily references World 1-2 and is based upon underground levels in general.

Mondo 1-2 (Super Mario Bros.)