From the Super Mario Wiki
The Block Fort is a battle course in the Mario Kart series. It first appeared in Mario Kart 64 with four structures in each corner of the level. Ramps lead up to the first level, where thin bridges lead to the other forts. Another ramp leads to the top level, with longer bridges to the other forts roofs.
A possible tactic is to plant Bananas or Fake Item Boxes on the thin ramps to crash players and to stay above the ground level where Green Shells could be flying. Item Boxes are on the ground levels edge-wall, and on both of the forts levels.
 Instruction Manual Description
The map consists of a series of floors, each three levels high. The four blocks are colored red, yellow, green and blue so you can quickly check your opponents' screens to find their locations.
 Names in Other Languages