The earliest traces of settlements along the course of the Tundzha River and its tributaries date from the 7^th century B.C. The remains of two big settlement mounds called Marcheva and Rasheva are located in the present-day town of Yambol. The finds discovered in them date from such distant times that it’s hard for us to imagine them – the Neolithic, the Chalcolithic and the Bronze Periods. A great part of the exhibits are kept in the Louvre (Paris) and in the Archaeological Museum in Sofia as well as in Yambol’s Historical Museum. Today, megalithic monuments and dolmens (pre-historic tombs made of huge stone blocks) can be seen near the villages of Hlyabovo, Sakartsi, Balgarska polyana and others. The dolmen near Hlyabovo is the biggest and best preserved in Bulgaria and on the Balkan Peninsula. It is known as “Tsar’s Dolmen” (“Tsarski dolmen”). It is situated in the Byalata Treva locality. It is big two-chamber dolmen, equipped with a dromos (corridor) and a façade. Well preserved are the lids of the two chambers and the mould that leads to them. Near the village of Kabile, which preserved the name coming from the glorious Thracian times, there’s a unique archaeological reserve bearing the same name. It includes remains of an ancient Thracian city, a Thracian rock sanctuary, remains of a Roman sanctuary and an archaeological museum, altogether spanning over a 500-decare area. Historical documents available today point that in the 4^th century B.C. the city was designed like the Greek cities – poleis with an acropolis, temples and a square, well protected behind fortified walls and towers. However, it is known that there was a settlement upon these lands in the Early Bronze Period. There are objects found which date from the 10^th-6^th century B.C. At the beginning of the 3th century B.C. Kabile was capital of the Odrysian Kingdom. The settlement was repeatedly attacked and conquered because of its key location. It existed until the 6^th century when it was destroyed by the Avars. During the glorious years of Kabile another settlement appeared under the present-day town of Yambol. Gradually, it took away Kabile’s functions and became a main centre of administrative, economical and religious affairs in the Southeastern Thrace.

The abundance of sites which are worth seeing in this region includes the unique rock temple of the sun which has hundreds of discs carved in the stone, symbolizing the sun rays. It is located near the village of Paleokastro, Topolovgrad Municipality and dates from the end of the 2^nd and the beginning of the 1^st century B.C. Similar sanctuary can be seen in the area of the village of Melnitsa.

This part of Bulgaria is also rich in fortresses, settlements, cult buildings and monastery complexes from the time of the Second Bulgarian Kingdom. Numerous ancient traditions, crafts and rituals have been preserved here. They can be seen during the various folklore festivals and gatherings which take place in the region.