In the original Super Mario Bros. NES game, there are several warp zones which are hidden areas that allow you to skip levels.

The first is hidden past the edge of level 1-2. Take the moving platform up until your character can jump on top of the brick ceiling. Once there walk to the right and you will eventually fall into a room with three pipes which lead to levels 2, 3 and 4.

The second is toward the beginning of level 4-2. Stand under the three bricks which are to the right of the first moving platform. Jumping up will reveal hidden blocks which can be jumped upon. Use the extra height to hit the first of the three bricks and a beanstalk will appear. Climb the beanstalk and you will be taken to a level of coins. At the end of this level you will find yet another room with yet another three pipes which this time lead to levels 6, 7 and 8.

And the final warp zone is at the end of level 4-2 and similarly to the first you simply have to break through the ceiling and run atop of it until you are taken to a single pipe which leads to level 5.

At each warp zone there is a greeting message: "WELCOME TO WARP ZONE!" and markers over each of the pipes denoting to which levels they lead.