If not an entire postcard, the above is at least a half a postcard of Churchill Downs, home of the Kentucky Derby, and among the most famous horse racing tracks in the US, if not the entire horse racing world. It is also known for being the first race course to host a Rolling Stones concert in 2006.
This short series on race tracks led me to wonder about horse racing elsewhere in the world. Turns out thoroughbred breeding started in England, and expanded to France, the US, Argentina, and much later, Japan. There are race tracks (frequently called "hippodromos" in non-English speaking countries) in at least 44 countries. (For a complete list, see here.) Given the specialist postcard collections I've stumbled across, I don't doubt that somewhere there is a deltiologist specializing in race courses worldwide.
P.S. It's Postcard Friendship Friday. The big question is, how did we get to another Friday so fast?