Here’s what you’ll learn when you read this story:

• A discovery of a 6,300-year-old megalithic grave site in central Iberia recalibrates the history of funerary tradition.
• The tombs at the Valdelasilla site in central Spain were enclosed by an impressive ditch and made from a mix of wood, clay, and stone.
• Discovery of a distinct megalith so far away from coastal sites shows that inland people had their own architectural know-how.

Starting around 4500 B.C.E., communities across western Europe began building massive stone tombs for their dead that we call megaliths. These monuments dot the Atlantic coastline and Mediterranean shores, and for decades archaeologists believed the tradition was spread by seafaring peoples who passed the practice from port to port. The prevailing model, supported by radiocarbon dating and Bayesian statistics published in a landmark 2019 study, pointed to northwestern France as the single point of origin, with the practice radiating outward via maritime routes. Inland regions, including the vast plateau at the heart of the Iberian Peninsula, were treated as latecomers—places that received the megalithic concept only after it had already matured on the coast.

That narrative just got a lot more complicated. Archaeologists have discovered a megalithic cemetery in central Spain, hundreds of kilometers from the nearest shoreline, that dates to roughly 4300 B.C.E. The site, called Valdelasilla, sits on a gentle hillside near the town of Illescas in the province of Toledo, in the flat, dry basin of the Tagus River. It’s the same age as Europe’s oldest coastal megaliths, meaning that inland peoples were building permanent monuments to their dead without any outside influences.

In a new study published in the Cambridge Archaeological Journal, Rosa Barroso Bermejo of the University of Alcala and her colleagues show how the funerary practices at the Valdelasilla site in central Spain prove the area had an autonomous ability to carve out megalith structures. “The location of the necropolis offers new insights into the role of inland regions in the emergence of Iberian and European megalithism,” the authors wrote.

The main circular funerary chamber of the Valdelasilla tomb spans about 20 feet across, tucked inside a circular ditch of over 115 feet in diameter, both with matching southeast-facing entrances. Radiocarbon dating of 21 bones from 46 individuals discovered in 11 different graves established that the first phase of the five-phase cemetery was built around 4300 B.C.E. Smaller tombs surrounded the largest one, and additional graves were added to the site over time.

The design wasn’t modeled after a classic stone megalith, instead using timber posts, compacted clay walls, and small stones to create sealed chambers as distinct spaces for the deceased. “The burial chambers, although built with walls of wood, clay, and small stones, are far from rudimentary and were designed for permanence and for visibility,” the authors wrote.

The chambers are notably different from the typical pit graves of most early and middle Neolithic burials in the interior of the Iberian Peninsula. The central tomb at Valdelasilla is the most impressive structure, but the site changed over 1,500 years due to evolving funerary practices. The earliest phase featured small chambers holding just a few individuals each, while later phases saw the central tomb—which first contained just two individuals—grow to contain the remains of 10 people. Other tombs included double and triple burials.

An ossuary holding 17 people was later added to the site. In total, the remains of 46 men, women, and children show how the stable population established in the fifth millennium changed the funerary landscape, giving us the “earliest known monumental necropolis in the interior of the Iberian Peninsula,” as the authors put it.

Many of the skeletons showed evidence of red iron oxide pigment, which was commonly used in funerary rituals in Iberia. Alongside human remains, archaeologists recovered bone hairpins, stone beads, flint microliths, polished axes, pottery fragments, evidence of burning, animal remains, and as many as 100 seashells. The grave goods, apart from the seashells, are considered local materials. The lack of Bell Beaker pottery shows that Valdelasilla was established before that culture swept into the area.

The Valdelasilla site poses a serious challenge to the dominant theory that monumental burial traditions originated in a single coastal region and radiated outward along sea routes. If a community on the landlocked Spanish plateau was independently designing megalithic tombs at the same time as groups on the Atlantic and Mediterranean coasts, the France-first diffusion model breaks down. “Instead of having a single point of origin, the emergence of megalithism in Europe appears to follow a multiple model of interconnected regions involving not only the coast but also continental areas,” the authors wrote.

That conclusion has implications well beyond Iberia. Megaliths stretch from Scandinavia to North Africa, and the question of whether that tradition spread by migration, trade networks, or independent invention is one of the oldest debates in European archaeology. Valdelasilla offers hard evidence that at least some inland communities created megaliths on their own. For researchers trying to understand how complex societies first emerged in prehistoric Europe, it’s an important demonstration that there many not be a single origin story, after all.