If you look closer at the level design, each part of it is from a past Mario Kart title. Below is a list of some of the references to all the previous games in the franchise:
1. The track layout/the neon sky outlines are from Mario Kart 64.
2. The City underneath the course is from Mario Kart: Double Dash.
3. The actual floors are from the classic Super Mario Kart.
4. The side-wall of the course are seen originally in Mario Kart DS.
These aren’t the only easter eggs. If you know any of the others be sure to let us know in the comments below.