The Dolmen de Guadalperal, in the Spanish province of Cáceres, becomes an international sensation, dubbed “the Spanish Stonehenge,” every time a drought leaves its stones exposed above the waterline.
The trouble is that in strictly archaeological terms, the comparison is wrong.
Stonehenge is a cromlech—a circle of standing stones. Guadalperal is a dolmen, a funerary chamber with a roofed entrance corridor.
They served different purposes and were built on different principles, even though both are made from vertical stones driven into the ground.
Not the Monument Most People Picture
The structure at Guadalperal consists of more than 150 vertical granite slabs called orthostats.
Thirteen of them form an oval chamber roughly 16 feet in diameter, preceded by an entrance corridor about 69 feet long.
That design, typical of the western Iberian Peninsula, is technically an anta-type dolmen, and its original function was almost certainly funerary.
Some researchers, however, believe it may also have served a religious or commercial role, since it sits near one of the few reliable crossing points on the Tagus between north and south.
A Chance Discovery on a Summer Estate
The monument first came to light in 1925, when German archaeologist Hugo Obermaier—spending the summer at a nearby estate as chaplain to the House of Alba—stumbled across the cluster of stones.
He excavated the site between 1925 and 1927.
Decades later, in the 1950s, the husband-and-wife archaeologists Georg and Vera Leisner gathered and organized the scattered records divided between the University of Freiburg and the House of Alba’s archives.
Then in the 1990s, researchers Primitiva Bueno Ramírez and Rodrigo de Balbín Behrmann returned to the site and published a detailed study of the engravings found on one of its principal stones.
The Menhir That May Be the World’s Oldest Map
That central stone—a menhir standing roughly 6.5 feet tall at the entrance to the chamber—holds much of the site’s mystery.
Carved into its surface is a sinuous line that most experts interpret as a serpent, a common protective motif in the megalithic art of the region.
But Ángel Castaño, a resident of the nearby town of Peraleda de la Mata, proposed a different reading: that the line is not a serpent at all, but a 9-mile stretch of the Tagus River between two of its tributaries.
If confirmed, it would rank among the oldest realistic maps ever known.
That said, no formal scientific consensus supports the idea beyond the visual resemblance Castaño himself pointed out.
Drowned by a Political Decision
In 1963, during Francisco Franco’s dictatorship, the government flooded the area as part of the construction of the Valdecanas reservoir on the Tagus River.
The dolmen wasn’t the only heritage site lost to the project.
The ancient Roman city of Augustobriga was also lost, and only a handful of its arches were rescued and relocated before the valley was flooded.
Since then, the monument has resurfaced in full only a handful of times, always during severe drought.
The best-remembered of these came in the summer of 2019, when NASA satellites captured images of the nearly empty reservoir and the site reappeared after 50 years underwater.
In 2022, an even more intense drought—with the reservoir at just 28% capacity—left the dolmen fully exposed and drew the international media coverage that once again spread the “Spanish Stonehenge” nickname.
What began as an occasional curiosity has since become almost a seasonal ritual.
Since 2019, the dolmen has tended to rise back into view each July and slip below the surface again around September, when autumn rains restore the reservoir to normal levels.
That predictability—greater than its ghostly reputation might suggest—makes it no less fragile. Each cycle of drying and flooding continues to wear away the same porous granite that experts have spent years trying to protect.
An Unresolved Dilemma
Each time it resurfaces, the same debate reopens: leave the dolmen where it is, or move it to dry land.
The local association Raíces de Peraleda filed a public petition to have the monument moved to a museum, arguing that the constant cycles of flooding and drying are fracturing the porous granite—damage that worsens with every visit from curious tourists.
Spain’s Ministry of Culture and the regional government of Extremadura have so far leaned toward leaving it in place, after several specialists warned that moving it could cause far greater—and irreversible—harm than leaving it underwater.
While that decision remains unresolved, the dolmen stays where it has been for more than sixty years: underwater most of the time, waiting for the next drought to bring it briefly back into the light—if only for a few weeks. Its stones were once part of daily life for a community that vanished five thousand years ago.
