Archaeologists are staging a major expedition to the south eastern slopes of Kozi Gramadi peak in Sredna Gora to investigate the only fortified residence from the era of the Odrysian Kingdom in Bulgaria, the National Museum of History in Sofia said in an official press release on June 6 2011.

The residence is in the village of Starosel vin Hisarya municipality.

The kingdom was formed by a union of Thracian tribes that lived between the 5th and 3rd centuries BC.

The territory of the Odrysian kingdom included largely present-day Bulgaria spreading to parts of northern Dobroudzha, parts of northern Greece and present-day Turkey.

Bulgarian archaeologists discovered the fortified residence in 2005 and in 2010 excavations were restored.

The expedition starts in June 2011 and will last three months.

The team of scientists headed by archaelogist Ivan Hristo includes Dr Hristo Popov from Bulgarian Academy of Sciences, Daniela Stoyanova a researcher from Sofia University and Valentin Todorov from National Art Gallery, Sofia.

The scientists will have the unique opportunity to excavate the interior area of the Thracian residence, which was built during the reign of Teres I (351-341 BC).

The ancient culture of the Odrysians is a curious mixture of Thracian local tradition and Greek influence. Monumental architecture and object from the dawn of Hellenic era are found in the residence.

Hristov's team will also try to conserve the historically important fortified residence.

The expedition is financed by Lachezar Tsotsorkov, the National Museum of History in Sofia and Hisarya municipality.