The D5 Race Track was made using Blender and has been extensively tested in Unity.
// This package contains :
1. The track in 2 formats : .fbx & .obj.
2. Prefab with all materials & colliders set up.
3. Showcase scene.
Colliders have been provided for the barriers and the racetrack mesh has been divided into two part.
Also has Low-Poly vegetation along the track and a couple of misc. buildings.
// Mesh Info :
Poly Count : 385,043
Vertices : 556,332
No. of Objects : 25
For more info, email me.