Where in the body do you experience heartburn?

The correct answer is in the esophagus.

Heartburn is a burning sensation in the chest, just behind the breastbone. It is caused by stomach acid flowing back into the esophagus. The esophagus is the tube that carries food from the mouth to the stomach. When stomach acid comes into contact with the lining of the esophagus, it can cause irritation and inflammation, leading to the sensation of heartburn.