The Ancient Thracian Cromlech (Stone Circle) in the town of Staro Zhelezare – also known in the media as “the Bulgarian Stonehenge" – is a an Ancient Thracian megalithic observatory located 12 km away from the southern Bulgarian town of Hisarya, and 10 km southeast of the Thracian cult temple at Starosel. The Ancient Thracian cromlech in the town of Staro Zhelezare consists of 24 erect megalithic slabs (of which 2 are missing) of various sizes arranged in a proper circle. They are believed to have been used by the Odrysians (Odrysae), the most powerful Thracian tribe which created the Odrysian Kingdom. The stone circle was covered buried under a man-made mound known today as Cholakova Mogila by the Thracians after they stopped using it. The mound itself is 45 meters in diameter, and the stone circle measures 6 meters in diameter.
The Staro Zhelezare Cromlech (Stone Circle) was discovered in 2001 by late Bulgarian archaeologist Georgi Kitov. Fragments of ceramic vessels found after digging up the mound above the cromlech were dated to the beginning of the 5th century BC, while the cromlech (stone circle) itself is dated to the 6th century BC. It is the only cromlech (stone circle) of its kind found in the northern part of today’s historical and geographic region of Thrace (Trakiya) known as Upper Thrace. Similar stone circles have been found in the very south of Bulgaria – in the Eastern Rhodope Mountains and in the Strandzha Mountain. Archaeological and astronomical research indicates that the cromlech (stone circle) near Staro Zhelezare was used by the Ancient Thracians as an astronomical observatory to measure the year cycle, equinoxes, and solstices which played an essential role in the rituals and economics in the Thracian calendar. The different phases of the Sun God were followed by the Thracian priests while the regular Thracians provided sacrifice gifts.
Cromlech (from Welsh) is a term describing prehistoric and ancient megalithic structures. In English, it usually stands for dolmens, prehistoric single-chamber stone tombs. However, in some other European languages, including Bulgarian, French, Spanish, or Italian, cromlech stands for prehistoric megalithic structures known more commonly known in Enlgish as stone circles.