Rainbow Road is a stage that has appeared in every Mario Kart game to date, although it changes every game. It is always the last stage in the Special Cup, and is often the most difficult and one of the longest courses. It also has many hazards and boosts, making it very hard to steer. It is the most recognizable track in the Mario Kart Series.
Super Mario Kart featured the first Rainbow Road. The course was completely flat, and featured seven 90 degree turns. Along the course, Thwomps would fall on you as obstacles. The tiles would flash in the colors of a rainbow. There were no rails.
It would reappear in Mario Kart 7 as the final race for the Lightning Cup. The Star Thwomps make a return in this game and when they hit the ground, they will shake the road which allows the player to do tricks off of. There would be ramps added throughout the course as well.
In Mario Kart 64, Rainbow Road was the longest stage in the game, and the longest track in the entire series to date. In the background were stars which made the face of all of the characters in the game. In the stage were Chain Chomps which would travel the opposite way as you, and try to hit you off. There is a glitch in the course were if you jump at a certain point you land much further down on the course.
In Mario Kart Super Circuit Rainbow Road was a fairly basic course. Instead of walls, for the most part there were jump rails. It was possible to use those jumps to your advantage and get big shortcuts.
A remake of the Rainbow Road from Super Mario Kart appeared in this game as well. In the remake, instead of thwomps hitting you, stars would fall and hit you.
In Mario Kart: Double Dash there are tight turns all along the course with boosts on them, making it hard to steer at the speed you are going at. Every once in a while, stars will fall from the sky, and can be picked up for invincibility. There is also a pipe which will will bring you to the top of the course, as the rest of the course is slanted down.
The Rainbow Road in Mario Kart DS was the first Mario Kart course to ever go upside-down. In the course, there is both a corkscrew, and a loop. Unlike all the rest of the Rainbow Road's, the stripes on the track run vertically, not horizontally. Although there are no obstacles on this track, it does have a lot of tight turns and drops so it is just as difficult to drive on as any other. The loops are also a big hazard as if you hit an item while you're upside down you will fall off the track, losing yourself valuable time and possibly some position slots.
The Rainbow Road in Mario Kart Wii is partially related to Super Mario Galaxy. Star Bits can be seen in some parts of the track. Also, in the middle of the course, there is a launch star made to resemble that of Super Mario Galaxy. The track contains two circles in a row, and it is possible to jump the middle with a Golden Mushroom. There is also a section where you go off one ramp, and land on another. Underneath the track, a planet can be seen, although it is unknown which planet it is.
Rainbow Road would have a new incarnation in Mario Kart 7 as the final track for the Special Cup. It is made up of multi-colored tiles and shows off planets and rockets in the background. It would feature one lap instead of three as it is divided into three sections that resemble laps, with banners at the end of each section.
Unlike the past Rainbow Road tracks, this Rainbow Road will have the player driving on non-rainbow tile surfaces like the moon and rings of a planet. The first part of it has the racers driving on rainbow tiles, while the second part has them racing on the rings of a planet for a small amount of time. The third part will send the to the moon with Chomps coming out of the craters. Like Mario Kart: Double Dash!!, the music for this track is a remix of the Mario Kart 64's Rainbow Road.
 In Other Games
In both arcade versions of Mario Kart (Mario Kart Arcade GP and Mario Kart Arcade GP 2) There are courses named Rainbow Coaster and Rainbow Downhill. Although not exactly Rainbow Road, they each resemble it.
In Mario Hoops 3 on 3, a court is called Rainbow Road. The stripes run vertically like Mario Kart DS, and it is located over clouds. The court circles around a few very tall turrets on a castle.