A country often described to lie at the crossroads linking the East and West, Bulgaria was the centre of Slavic Europe during much of the Middle Ages, exerting considerable literary and cultural influence over the Eastern Orthodox Slavic world by means of the Preslav and Ohrid Literary Schools. Bulgaria is also the birthplace of the Cyrillic alphabet, the second most widely used alphabet in the world, which was developed in these two schools in the 10th century.
Bulgaria is well-known for its rich folklore, distinctive traditional music, rituals and tales, but the country's contribution to humanity also continued in the 19th and 20th century, when individuals such as John Atanasoff - born in USA with Bulgarian origin, regarded as the father of the digital computer, a number of noted opera singers (Nicolai Ghiaurov, Boris Christoff, Raina Kabaivanska, Ghena Dimitrova) and successful artists (Christo Javacheff, Pascin, Vladimir Dimitrov) popularized the culture of Bulgaria abroad.
A number of ancient civilizations, most notably the Thracians, Greeks, Romans, Slavs and Bulgars, have left their mark on the culture, history and heritage of Bulgaria. The country has nine UNESCO World Heritage Sites. Of these, two are Thracian tombs (one in Sveshtari and one in Kazanlak), three are monuments of medieval Bulgarian culture (the Boyana Church, the Rila Monastery and the Rock-hewn Churches of Ivanovo), while the Pirin National Park and the Srebarna Nature Reserve represent the country's natural beauty, and the ancient city of Nesebar is a unique combination of European cultural interaction, as well as, historically, one of the most important centres of naval trade in the Black Sea. In addition, the Varna Necropolis, a 3200-3000 BC burial site, contains what are believed to be the oldest examples of worked gold in the world.