What is a unique feature of the Kentucky Derby?

The Kentucky Derby is unique because it exclusively features Thoroughbred horses, which are a specific breed known for their speed and agility. This race is a significant part of American horse racing culture and is recognized as the longest-running horse race in the United States. Held annually at Churchill Downs in Louisville, the Derby showcases the athleticism and breeding of Thoroughbreds, making it a premier event in the horse racing calendar.

Other options do not accurately represent the characteristics of the Kentucky Derby. For instance, the Derby isn't held in winter; it takes place on the first Saturday in May, which occurs in spring. Additionally, while events can have various influences, the Derby does not have a direct significance in international politics. Lastly, it is held outdoors at a historic racetrack, not in an indoor arena, which is a critical aspect of its atmosphere and tradition.