The Elder Scrolls III: Morrowind/Pegas Ranch

Pegas Ranch layout
Pegas Ranch is located in the Grazelands Region, directly south of Vos (but if you hit Tel Vos you've come too far).

Horse breeding chain
Like Pokémon, Pegas Ranch features rare breeds that can only be gained via breeding. The horses in the far-left column are the first evolution, and are the only ones that can be purchased. The others are accessible via breeding only.