According to some researches, the Slavic population was already assimilated before the end of the Dark Ages. According to some studies, the area was part of the First Bulgarian Empire between 681 and c.1000. While maintaining commercial links with the Byzantine Empire (as attested by the excavations of 9th–12th century Byzantine coins at various locations), the area was subject to the successive invasions of Pechenegs and Cumans and conquered by the Mongols during the 1241 invasion of Europe. It was probably later disputed between the Magyars and Second Bulgarian Empire. According to a legend first attested in the 19th century, the city was founded by a shepherd named Bucur (or, alternatively, a boyar of that same name). Like most of the older cities in Muntenia, its foundation has also been ascribed to the legendary Wallachian prince Radu Negru (in stories first recorded in the 16th century). The theory identifying Bucharest with a "Dâmboviţa citadel" and "pârcălab" mentioned in connection with Vladislav I of Wallachia (in the 1370s) is contradicted by archaeology, which has shown that the area was virtually uninhabited during the 14th century. Bucharest was first mentioned on September 20, 1459, as one of the residences of Prince Vlad III Dracula. It soon became the preferred summer residence of the princely court – together with Târgovişte, one of the two capitals of Wallachia – and was viewed by contemporaries as the strongest citadel in its country. In 1476, it was sacked by the Moldavian Prince Stephen the Great, but was nonetheless favoured as a residence by most rulers in the immediately following period and was subject to important changes in landscape under Mircea Ciobanul, who built the palace and church in Curtea Veche (the court's area), equipped the town with a stockade, and took measures to provide Bucharest with fresh water and produce (early 1550s). When Mircea Ciobanul was deposed by the Ottoman Empire (Wallachia's overlord) in the spring of 1554, Bucharest was ravaged by Janissary troops; violence again occurred after Mircea returned to the throne and attacked those who had been loyal to Pătraşcu cel Bun (February 1558), during the 1574 conflict between Vintilă and Alexandru II Mircea, and under the rule of Alexandru cel Rău (early 1590s).