According to Carl's Sims 3 Guide, "Sims attracted to it will have traits like loves the outdoors, equestrian and animal lover or be a horseman/woman. Sims with riding, jumping and racing skill will also frequent the ranch. Sims who hate the outdoors will not go there. You can hold a party at a horse ranch."
See also: Cat Jungle, Dog Park.
World: Appaloosa Plains
Name: Equestrian Regional Training Grounds
Size: 60 x 60
Cost: $64,582