Bulgaria has by now seven cultural and two natural sites included in the UNESCO List of the World Natural and Cultural Heritage: The Madara Horseman (the only rock relief from the medieval times in Europe); the Kazanlak and Sveshtari Thracian Tombs (4th and 3rd century BC); the Rila Monastery; the Boyana Church near Sofia; the Rock-hewn churches of Ivanovo (dug out of the limestone cliffs and inhabited until the 17th century); and the ancient city of Nessebar on the Black Sea coast. UNESCO recognizes also Pirin National Park and Srebarna biosphere reserve for their incredible biodiversity.