Here's an explanation of all courses in Mario Kart: Pro Circuit
A basic course made of asphalt. There are no obstacles on the road.
A peaceful valley with a lot of flowers. It resembles some Yoshi's Island levels.
A race track around Peach Castle. The player will race through Toad Town and around Peach Castl itself. At the entrance of the castle, Rabbits hopping around making it hard to pass. The castle resembles the one from Super Mario 64, and the player will go through almost every room of the castle. Near the end of the lap, the player is shot out of the castle using a cannon.
A course resembling Bob-Omb Factory from Mario Party 9. A lot of Bob-Ombs will block your way as you try to avoid many other obstacles. Some mechanical parts of the MKDS course Tick Tock Clock will return as moving parts of the course.
Toadette's Music Room
A musical room with giant, magical music instruments. It resembles the board from Mario Party DS.
A beach-themed course resembling the hub from Super Mario Sunshine. This course is one of the few 1 lap-courses of the game. The player starts on top of Carona Mountain, and ends in Ricco Harbor (you can get there using a cannon).
A basic course with many Piranha Plants and Goomba's. In the distance you can see Peach's Castle.
Speedy Comet Island
This course resembles some of the Speedy Comet levels from Super Mario Galaxy. There is a fiery part, a desert part and an icy part. Many enemies from Super Mario Galaxy can be seen in the background.
The player starts in a small village full of wooden, little houses. When out of the village, the player races into a big forest, slightly resembling Tall Trunk Galaxy from Super Mario Galaxy 2. Many Pianta's can be seen in the background. At one part, Giant Wigglers will blocking the road.
A course resembling Honeyhive Galaxy and Honeyhop Galaxy. The player starts at Honeyhive Galaxy (referred as Honeyhive Kingdom in this game). Using a launch star-like cannon, the player is shot to the other part, more resembling Honeyhop Kingdom. The finish is were Queen Bee was in Super Mario Galaxy. The course only counts 1 lap.
A course resembling Super Mario 3D Land. The player starts in a World 1-like landscape, and, using different ramps, races through other landscapes, resembling various levels of this game. Near the end, the player will enter Bowser's Castle. At the end of the castle, the player will race through a remodeled version of the Final Battle stadium. At the very end near the finish, it's like the player is in World 1 again. There will be a flagpole near the finish, which turns gold when someone passes it.
A dark course with many giant books as obstacles. It resembles the board from Mario Party DS.
A huge, bussy city with heavy traffic. It slightly resembles Moonview Highway and Mushroom City. Near the end, the player will race through a part resembling Koopa City from Mario Kart 7.
Mc Ballyhoo's Tycoon Park
A giant amusement park, slightly resembling the Star Carnival from Mario Party 8. The player can see many attractions like a giant Roller Coaster.
Bowser's Castle resembling the one from New Super Mario Bros. Wii. It's a really hard and long course. A Metallic Bowser will spit giant Fireballs all the time blocking the way. The course is surrounded by lava, at some parts making it hard to not fall in it.
The classic Rainbow Road off course makes it's return. And again, it counts only 1 lap. The player starts above a city with many skyscrapers. Using a so called 'Rainbow Jump' the player will get launched into space. Many planets, including the moon and some galaxy's from the Super Mario Galaxy series, can be seen in the background. At some of the planets, the road just runs about it, causing an anti-gravity effect. The finish will be on a bright and shiny planet, slightly resembling the sun.