I have a memory of a soporific summer’s day, sitting in a medieval history lecture hearing the tale of the capture of Baldwin of Flanders when Tsar Kaloyan defeated the Army of the Latins.

Close to 30 years later, on another hot summer’s day, and I am at the foot of the 18m high walls of the fortress on the site where Baldwin is said to have been captured on that April day in 1205 CE.

From the hill on which Bukelon Fortress stands, just outside the tiny Bulgarian village of Matochina, a tiny red dot may be seen atop a building in the valley below – a Turkish flag, denoting where today’s border stands in an area long contested.

In the fourth century, the Goths routed emperor Valent’s army on this spot, with Valent being killed in the clash. Bukelon, in its times, is believed to have served variously not only as a fortress but also in Ottoman times, a jail and an administrative centre. It is also said to have done duty as a church.

There may be earlier foundations below, from the times of others who held this hill with its breathtaking lookout, likely even from Thracian times. Those who have stood watch over the horizons include Byzantines, Ottomans and Bulgarians. Today, not far away, stands one of a series of spindly metal towers built by the Bulgaria of the immediate past to keep watch over its Nato member neighbour. In the distance, Edirne; Bukelon’s brief was for hundreds of years to be a guardian sentinel protecting the Turkish town.

What remains today is the inner part of the fortress with a keep with arrow loops.

Matochina is 40km from Svilengrad and 110km from Haskovo, in the region of Sakar which, while today renowned for its wines, has a wealth of archeological and historical treasures, not only Bukelon but also relics of Thracian times – dolmens, and near Topolovgrad, Paleocastro – said to have been a Thracian sacred site and which has intriguing rock circles, as well as churches hollowed out from the very stone, the work of Christians in the 10th century.

Paleocastro is said to date from sometime in the 10th to fifth century BCE, a sun worship site for the Thracians. Atop the hill, reached after a rigorous walk up through the trees, shades of blue, green and indigo stretch out across the Sakar landscape. Even today, there are those who believe that the rock into which the mysterious circles were carved hold a special energy that emanates from trace metals within the sun-baked stone.

Sakar is especially rich in dolmens, and regularly more such remains from Thracian times are discovered. We were taken to several in the Sakar region by minibus, courtesy of the State Agency for Tourism and the Bulgarian Association for Alternative Tourism. A few may be found by the roadside but others are in the woods and while signposted, it is better to make contacts in towns or through websites to draw on local knowledge and guides.

The dolmens are believed to date from the early Iron Age, from the 11th to sixth centuries BCE, and typically are constructed of huge hewn shapes of stone placed together to form low-rise structures, which, archeologists tell us, served as tombs. Currently, more than 70 dolmens are known in the Topolovgrad area, all about 3200 years old, but more may yet lie undiscovered in the woods or elsewhere on some high plateau – sights with panoramic views seem to have been popular choices for whatever forms of ritual worship were practiced by the Thracians.

Some archeologists hold that the areas where the dolmens are found, not only Sakar but also the Eastern Rhodopes and Strandja, were occupied by the Odrisi, a Thracian tribe, agriculturalists (said also to have developed metallurgical skills, hence the precious metals legacy on display in Bulgarian museums) who lived variously in relatively large communal settlements and otherwise in much smaller villages.