Large and small, isolated or in groups, you will see mounds all over Bulgaria: atop rolling hills and amid farming fields, by old village graveyards and motorways, even on the outskirts of Sofia. The ancient Thracians who lived in the Bulgarian lands between the 1st millennium BC and the 6th century AD created most of them. They buried their dead there, interring noblemen and women with expensive personal possessions. In many cases the tombs were very impressive, such as those in Kazanlak, Aleksandrovo and Sboryanovo.
Among the 30,000-plus mounds that exist in Bulgaria today, one stands out. Even when it was yet to be excavated, every archaeology student knew its name: Maltepe. Located at Manole Village, near Plovdiv, it is the largest mound in Bulgaria, at 26 metres high and with a diameter of 140 metres.
Maltepe's sheer size suggested that the lucky archaeologist who got to excavate it would probably find inside the tomb of some very important Thracian noble, a discovery that would make headlines and build careers.
In the 2010s, Dr Kostadin Kisyov, director of the Archaeological Museum in Plovdiv and an established researcher of Thracian burial sites, did just that. What he discovered indeed made the news. Significantly, it was a surprise no one was prepared for.
The 80,000-cubic-metre Maltepe mound does not contain graves, tombs, burial artefacts or human remains. Instead, a massive structure of stones stands in its centre. Its size is remarkable: it is 23 metre high and each side of its square base is 9 metres long. No such structure has ever been found in an ancient Thracian mound.
The sheer size of the structure is stunning
Suddenly, the identity and the intentions of the creators of Maltepe Mound became a mystery.
Upon learning the news, the mainstream Bulgarian media rushed to generate outlandish "theories," claiming that Maltepe was the tomb of Alexander the Great, of Rhoemetalces, a 1st century AD king of the Thracian Odrysian Kingdom, or of one of the many Roman emperors who fought to stay on the throne for more than a year during the tumultuous 3rd century. The most exotic "theory" so far has been that a whole "city of the dead," whatever that might mean, is still hidden beneath the stone structure. The word "pyramid" is also often used in sensationalist reportages from the site.
In reality, the structure in the centre of the Maltepe Mound is not a tomb at all. It does not contain any rooms. Instead, the whole massive structure is filled with stones. Archaeologists have discovered about a dozen pits, dug into the mound, containing artefacts from the 3rd century AD, probably placed there as part of religious rituals. A two-metre high wall of stones encircled the mound, ensuring its stability.
According to the most plausible explanation, the stone structure was the foundation of a gigantic sculpture that used to stand atop Maltepe. The mound was created both as an additional support for the structure, and to make the statue more visible. The area around is very flat and the hypothetical monument would be visible from afar, particularly from the nearby ancient road that connected Central Europe with the Bosporus and Asia Minor.
The statue might have commemorated an important battle, a larger-than-life demonstration of the might of the empire to the local population. A possible analogue could have been the Tropaeum Traiani in Romania, a monument atop a mound built in AD 109 by Emperor Trajan to celebrate his victory over the Dacians.
The statue that supposedly stood atop Maltepe, if ever there was such a thing, is long gone. Excavations are far from over, however, and the archaeologists hope that they will eventually find a definite answer to the question of what Maltepe was.
The people from the area, who for centuries have lived with the mighty and mysterious silhouette of Maltepe at their doorsteps, never suffered from such doubts. For them the mound's obvious purpose was to hide a gold treasure trove. Even the name of the mound points to this belief; in Turkish it means Treasure Hill.
Treasure hunting has been popular in the Bulgarian lands for centuries and most of the Thracian mounds in this country bear traces of this activity. Maltepe Mound was not spared either.
Sometime in the 16th century, a group of men started digging into the mound. They were professionals: they targeted the southern part of Maltepe as they were obviously aware that ancient Thracian graves are usually located in this part of a mound.
The treasure hunters dug, and dug, and dug, and then they hit a stone wall. We can only imagine their joy when they thought they had finally found the gold, and their disappointment when they discovered only more stones, solid and impenetrable, behind the wall.
In the end, the treasure hunters gave up and left. Five centuries later, Dr Kisyov's team discovered the traces of their fruitless effort: a long, wide tunnel, some droppings and the harness from the donkey they brought with them to carry the gold, and three coins minted under Sultan Suleiman that probably slipped from their purses.
Ironically, Maltepe Mound surprised the 16th century treasure hunters just as it did the 21st century archaeologists, and it will probably provide some more unexpected discoveries. Research is ongoing and the site is currently off-limits to the general public.