N64 Big Donut

Big Donut is a battle course in Mario Kart 64. As its name implies, the course is in the shape of a large donut. In the center hole of the donut is a pool of lava. If the players fall in it, they lose a balloon, and a Lakitu brings them out. There are also four rectangle-shaped blocks located around the course that provide a means to evade opposing racers and their items. The course is also slightly sloped inwards.

Mario Kart 7
Big Donut reappears in Mario Kart 7 as a retro battle course. In the game, the stage is given new elements. The blocks are now color-coded (red, blue, green, and yellow). There are jumping ramps so that players can use the gliders to fly over the pool of lava. The added Koopa Clown Car, floating in the center of the course, makes air currents so players can glide even higher. Lava springs often rise from the pool to plummet the players while gliding and make them fall into the lava. This is the only battle course in the game to activate the gliders.

Official descriptions
Mario Kart 64 instruction booklet: ''This map is in the shape of a big donut. Because there is no guardrail along the inside, should you make a mistake, you will dive into the lava. Use the four walls to hide and ambush your opponents.''

Mario Kart 64 web page: ''As its name suggests, Big Donut is shaped like a circle with a large hole in the middle. The course surface slopes up and away from the fiery central pit, and there are sections of wall situated around the track. Use these walls to hide from your opponent.''

Trivia

 * In Mario Kart 64, two item boxes can be seen under the course.