Plovdiv
Plovdiv, one of the oldest continuously inhabited cities in Europe, carries over 8,000 years of history layered into its streets. The Roman Theater, still in use today, was discovered by accident in the 1970s and now hosts operas and concerts overlooking the Rhodope Mountains. Nearby, visitors can walk the remains of a Roman stadium buried beneath the main pedestrian street, where modern shops and cafés stand above ancient foundations.