Bellow you can find information about some of the main archeological sites in Bulgaria

PERPERIKON
The ancient Thracian city of Perperikon is located in the EasternRhodopes, 15 km northeast of the present-day town of Kardzhali, Bulgaria, on a 470 m high rocky hill, which is thought to have been a sacred place. The village of Gorna Krepost ("Upper Fortress") is located at the foot of the hill and the gold-bearing Perpereshka River flows near it. Perperikon is the largest megalith ensemble in the Balkans.
It is thought that the famous sanctuary and oracular shrine dedicated to Sabazios (similar to Greek Dionysus) of the Bessi was situated there.A visitor centre is being constructed at a cost of 2.4 million Euros. Official site: www.perperikon.bg

   

TOMB OF KAZANLAK
The Thracian Tomb of Kazanlak (Bulgarian: 'Казанлъшка гробница') is a vaulted brickwork "beehive" (tholos) tomb near the town of Kazanlak in central Bulgaria.
The tomb is part of a large Thracian necropolis. It comprises a narrow corridor and a round burial chamber, both decorated with murals representing a Thracian couple at a ritual funeral feast. The monument dates back to the 4th century BC and has been on the UNESCO protected World Heritage Site list since 1979. The murals are memorable for the splendid horses and especially for the gesture of farewell, in which the seated couple grasp each other's wrists in a moment of tenderness and equality. The paintings are Bulgaria's best-preserved artistic masterpieces from the Hellenistic period.The tomb is situated near the ancient Thracian capital of Seuthopolis.

   

MADARA
Madara is famous for the Madara National Historical and Archaeological Reserve 1.5 km (0.93 mi) east of the village, one of the 100 Tourist Sites of Bulgaria. The reserve includes Neolithic and Eneolithic findings, a Thracian settlement, Ancient Roman villa and fortress from the 2nd–5th century, medieval Bulgarian palace, pagan sanctuaries, Christian churches and monasteries and fortresses from the First Bulgarian Empire. There is also a cave monastery from the 12th–14th century. Most importantly, Madara is the location of the famous Madara Rider, an early medieval (early 8th-century) large rock relief carved by the Bulgars and also featuring several epigraphs of historic importance written in Medieval Greek; the relief most likely dates to the reign of Tervel of Bulgaria.

   

TATUL
Tatul is a village in Momchilgrad municipality, Kardzhali Province located in the Eastern Rhodopes in southern Bulgaria.
In the 2000s Bulgarian archaeologists discovered an ancient Thracian surface tomb and sanctuary in the immediate proximity of the village, and it was soon recognized as an exclusive religious centre in the region of importance to the whole region according to head archaeologist Nikolay Ovcharov. Latest archaeological finds date the earliest settlement to 4000 BC

   
Source: Wikipedia