Rainbow Road

Rainbow Road is the final track in the Special Cup in all games of the Mario Kart series. The track is rainbow-colored and the course is suspended in space. It is well known for being one of the most surreal and toughest tracks to master, since most of the Rainbow Road tracks have no rails.

Super Mario Kart
The first Rainbow Road had no rails at all and contained 90-degree turns. The rainbow coloring is made of tiles, due to the limited graphical capabilities of the SNES. Flashing, invincible Thwomps serve as obstacles.

Mario Kart 64
This version of Rainbow Road contains rails throughout the course and roving Chain Chomps, which are half above the track, half below it, and follow the track reverse. There are neon-light pictures of the eight playable characters (plus a Boo and a Mushroom) in the distance, and a huge drop just after the start line. A carefully timed jump at the beginning could be used as a huge shortcut. It is the longest course in the series at two minutes a lap, or 2000 game meters.

Mario Kart: Super Circuit
In Mario Kart: Super Circuit, Rainbow Road has rails at the start line. Edges of the course are lined with bounce-jumps. Astute racers can use Mushrooms to perform significant shortcuts. The track has falling stars that can make racers spin out and Thunder Clouds that will shrink anyone careless enough to drive under them. The Bowser's Castle from Paper Mario can be seen in the background. This track is equal with the course of Rage Racer Overpass City. This game also features the Rainbow Road course from Super Mario Kart, but without the flashing Thwomps.

Mario Kart: Double Dash!!
Dash Panels give a boost of speed to the racers in the Mario Kart: Double Dash!! version of Rainbow Road. This version of Rainbow Road also has rails in parts of the course. It features a helix and a pipe that shoots players to the highest point of the track after reaching the very bottom. It also contains floating sculptures of items, and rains stars that racers can pick up. It has the most pearl-like colors of all the Rainbow Roads. Additionally, the entire course is placed high above a city. The city it floats over could be Mushroom City because of the design of some of the buildings. When in split screen mode, the city and the item sculptures are removed. The theme music played in the course is a remix of the Rainbow Road from Mario Kart 64, and reappears in Super Smash Bros Brawl as an alternative music theme for the Mario Circuit battle stage.

Mario Kart DS
The Rainbow Road of Mario Kart DS has several rails on certain curves and includes a loop and a corkscrew. Those elements may have been added to ensure challenge; players can place items so their opponents could fall off the corkscrew or the loop. Some multi-colored Pipes and Stars appears in the surroundings of the stage. Additionally, the coloring pattern of this looks different from the other previous Rainbow Roads: here, the stripes on the track follow along it, instead of crossing the track.

Mario Kart Wii
The Rainbow Road of Mario Kart Wii is a new version of the rainbow-colored track. The track is located over the Earth's stratosphere, mainly showing the eastern parts of North America, as well as parts of Europe, Africa, and South America. The course begins a 90 degrees slope, located once after the starting line. Multiple curves and trick pads appear, the course features also a launching point, where players are shot away by a stylized Launch Star. The track shows a reminiscent of the Rainbow Road of Mario Kart DS, while visual style is based on Super Mario Galaxy. Star Bits appear in the background of the course. A corkscrew reappears not far from that Launch Star. Further cementing the fact it was inspired from Super Mario Galaxy is the fact the ghost is Princess Rosalina, and a Launch Star pattern is seen on the rails.

Mario Hoops 3 on 3
Rainbow Road is the unlockable third dribble race from the "challenges" section in the basketball game Mario Hoops 3 on 3. However, this Rainbow Road floats above the clouds and around a clock tower, and not much of the course is fully seen when playing. Podoboos and Bombs come out of holes similar to Bowser Castle.

Trivia

 * F-Zero X has a track named Rainbow Road. It imitates the Mario Kart 64 version of the Rainbow Road, having the same map of the track, and following it basically. It is described as a "Psychedelic Experience". Parts, though not all of it, are rainbow-colored. Unlike the original, it has no barriers in certain areas, and the neon Mario series decor is missing - instead, it just has a plain black background with a watery blue bottom to which careless drivers may fall. In addition, when racing the track with the 64DD expansion features, the background song is a heavy metal version of the Rainbow Road song heard in MK64. Of course, there aren't any Chain Chomps.
 * Musician Mark Krump has written a tribute song to his deceased uncle titled Rainbow Road, the tune to which coincides with the BGM of the Rainbow Road of Mario Kart: Double Dash.
 * Rainbow Road is the only track in Super Mario Kart which is not numbered.
 * Sonic R has a Rainbow Road-like stage called Radiant Emerald. It flashes rainbow and, like rainbow road, takes place in space.