Sebring International Raceway
Like the Silverstone track in the UK, this is another track that has its history as an air base. Sebring International Raceway, located in Florida, USA, is the oldest permanent road-racing circuit in the United States. In 1952 the first “12-Hour Grand Prix of Endurance” was held, and 7 years later it was the site of the first United States Grand Prix.
The current track contains a mix of smooth asphalt-paved roadway and car-busting, tooth-rattling concrete-slab runways. It's common to compare the 12 hours of Sebring to the 24 hours of Daytona or the 24 hours of Le Mans by saying "it's half as long but twice as hard (on car and driver)".
The combination of long straights, corners ranging from wide-radius to a tight hairpin and the bouncing car makes it a challenge to find a good car setup. Not surprisingly, everyone refers to Sebring as "respect the bumps".
Some extra resources for a deep-dive: