Plovdiv is the second largest city in Bulgaria, situated on the Maritza River. Its unique location on these ancient crossroads has stimulated strong cultural and political influences from East and West civilizations, and yet maintained its unique cultural identity. Being older than most of the oldest towns like Rome, Athens, Carthage or Constantinople an almost contemporary of Troy, Plovdiv is a town built upon layers of towns and a culture developed upon layers of cultures. Plovdiv is a picturesque town, with many parks and gardens, museums and archaeological monuments. Its old part called the Old Town, with houses from the National Revival period (18-19th) is an imposing open-air museum situated on the three hills of the ancient Trimontium. One of the most remarkable sights of the town, the ancient Theatre (a well- preserved Roman theatre) is located there and is still used to open-air performances.