 Complete the following phrase:  The documented history of Strandzha dates back several millennia. The oldest traces of human habitation are stone axes and ceramic fragments found in the Ahtopol peninsula and are dated from the Neolithic period c. 60003000 BC. Since the mid-1st millennium BC the mountain was inhabited by the Thracian tribes Thyni and Asti and was part of the Odrysian kingdom. The Thracians of Strandzha were infamous for their pirate raids. By the 2nd century BC, the power of the Odrysian kingdom declined and it became a client state of the Roman Republic. However, it kept its independence until 46 BC, when it was annexed by the Roman Empire, forming the province of Thracia. The region remained part of the Roman Empire and its successor the Byzantine Empire. In Roman times, Strandzha was a centre of copper and iron ore mining and metallurgy. In the late 6th and early 7th centuries the Slavs settled in most of the Balkans, including Strandzha. The whole territory of the modern park was included in the Bulgarian Empire for the first time in the aftermath of the 