There’s an archeological site in present-day Turkey that is unlike anything we’ve ever found anywhere else in the world. There, around 12,000 years ago, a mysterious group of people—thought to have been hunter-gatherers—decided to build an intricate monument using multi-ton blocks of stone. By means we are still unable to comprehend, these mysterious people erected as many as 200 stone pillars in various walled circles. Some of the stones pillars at Göbekli Tepe have been found to weigh 10–20 metric tons and there is one pillar still inside its quarry with a total weight of over 50 tons.

Göbekli Tepe, which means potbelly hill, was discovered several decades ago, but like many other sites didn’t receive proper attention until one researcher decided to dig further and deeper revealed a secret buried beneath the surface.

The ancient site is located about 15 km northeast of the city of Sanliurfa (ancient city of Urfa), in the southeast of Turkey, near the border with Syria. Syria, interestingly, is home to some of the most ancient cities in the history of mankind, and precisely where some of the most ancient megalithic structures were ever built.

The first mention of Göbekli Tepe can be traced back to a survey conducted by archaeologists from the University of Istanbul and the University of Chicago in 19634. However, the buried megaliths were wrongly identified as grave markers, which led some experts to believe the site was actually a cemetery belonging to the Byzantine empire. Little did experts know that beneath the surface lay the remnants of one of the oldest, most complex temples on Earth.

The importance of the hill beneath which the ruins of Göbekli Tepe have remained hidden for millennia was only exposed when In 1994, Klaus Schmidt of the German Archaeological Institute decided to investigate the site further.

After having reviewed the archeological literature published during the 19634 surveys, Schmidt decided to visit and further investigate the site. Schmidt had previously been working at an equally important ancient site called Nevalı Çori. This site is located in the Şanlıurfa Province and is known among experts for being the site of some of the oldest known communal buildings and monumental sculpture on Earth.

Archaeological excavations at Nevalı Çori allowed Schmidt to recognized the similarities between the two sites, and that the stone blocks at Göbekli Tepe which were earlier mistaken for grave markers, may, in fact, be much more ancient prehistoric monumental works. Soon after Schmidt arrived at the site, he managed to excavate the first massive t-shaped pillar for which Göbekli Tepe is famous today.

The first pillar had proven that archaeological surveys of 1963 had missed a treasure trove hidden beneath the surface. Studies in the following years would eventually reveal that the tell which now stands at the site included two conclusive phases of use. Although we can’t possibly know the exact purpose of the site, experts believe Göbekli Tepe may have been of social or ritual nature.

Although we don’t know its exact, originally intended purpose, we know that the site is old. Really Old. Excavations have so far revealed that some of the oldest structures of Göbekli Tepe date back to around 10,000 BC.

This means that some 12,000 years ago, when hunter-gatherers roamed across Europe and hints of great civilizations such as that of Egypt were unimaginable, a mysterious group of people decided to stop at the site and erect a massive monument unlike any other. The sheer size of Göbekli Tepe is evidence of the massive undertaking of a construction project like it must have been for ancient people. The size of the stones and their intricately carved nature and placement bear evidence that the site, as well as the monument in general, was of great importance to ancient people.

Göbekli Tepe’s stratigraphy attests to countless centuries of activity, starting as early as the Epipaleolithic period, between approximately 20,000 and 10,000 years Before Present (BP). History books tell us that during this time, people were nomadic hunter-gatherers that lived in small seasonal camps and that there weren’t permanent villages. This period is defined by the appearance of microliths, small stone tools that were usually made of flint or chert, and around a centimeter in length and half a centimeter wide.

Göbekli Tepe serves as an ancient encyclopedia made of stone, and its structures are markers that now tell a long-lost story.

There are various periods in Göbekli Tepe’s timeline, the first being the Epipaleolithic. Structures identified in the succeeding period, the Pre-pottery Neolithic B are believed to be around 12,000 years old. The third complex of buildings belonging to the Pre-Pottery Neolithic B (PPNB) and dating from the 9th millennium BCE have also been unearthed.

This means that if the oldest structures at Göbekli Tepe were built around 10,000 BC, they are at least 7,000 years older than Stonehenge, and more than 7,500 years older than the Pyramids of Egypt.

The historical evidence offered by this ancient site asserts that the evolution of humanity at that time is just the opposite of what we thought. Contrary to popular belief, more than 12,000 years ago, people were sophisticated and organized enough to construct intricate ancient sites. They had enough knowledge that allowed them not only to survive the last ice age but also to develop tools and techniques that made it possible for them to quarry, transport and put into position multi-ton stones.

As revealed by Schmidt, and based on his discoveries at the site, “the coordinated effort for the construction of the monoliths created the basis for the development of complex societies.” In other words, in order to construct a monument, it was necessary to create the appropriate structure for its construction. The construction of such an ancient site tells us that the builders of Göbekli Tepe were a developed society that was able to provide not only food and shelter to the builders but also a sense of organization and hierarchy which must have been needed to build a site such as Göbekli Tepe.

The enigmatic stones at Göbekli Tepe tell a unique story. The megalithic stones are evidence of the ingenuity of long-lost megalithic builders, and similar ancient sites such as Nevalı Çori reaffirm the importance of Göbekli Tepe as a central gathering site of great importance.

Constructing a monument such as Göbekli Tepe some 12,000 years ago has about the same historical implications as the appearance of the first pyramids in Egypt. It was a never-before-seen undertake in human history, and its importance resides in more than just the stones. Erecting a monumental complex that is home to more than 200 7-ton pillars (each) raises various questions. It is not just about technology, it’s about the economic and social implications such a project has.

The construction of the site surely required a huge labor force, which in turn means that coordination and planning must have been well implemented. This leads me to believe that whoever was in charge of the construction process of Göbekli Tepe had to make sure the workforce was adequately equipped, well-fed and cared for.

Although we can’t possibly know how many people participated in the construction of the site, it surely required a large workforce. If so, how do you convince people, 12,000 years ago, that something the size of Göbekli Tepe needs to be built? How do you motivate them? According to the survey of the site as well as measurements of the stones, archaeologists have proposed that up to 500 persons were needed to remove the heavy pillars from their respective quarries and transport them between 100 and 500 meters (330–1,640 ft) to the site where they were placed.

This leads us towards another mystery: why? Why did someone decide to build such a vast complex in the first place? What was the site’s meaning? Purpose? What exactly do the countless symbols and motifs etched on the pillars signify?

Was the ancient monument used as a temple? Or is it possible that it was used as a kind of early astronomical observatory, through which the ancients charted maps and kept a record of time?