The so-called “Dolmen of Menga” on the Iberian Peninsula in Antequera, Spain was acknowledged as a groundbreaking discovery shortly after the first explorations were undertaken in the 1840’s.
With the originality of design, three pillars aligned with the central axis of the monument, and the massive size of the orthostats and capstones. Its extraordinary dimensions demanded sophisticated design and planning, a large mobilization of labor, as well as perfectly executed logistics.
Once inside Menga, it becomes readily apparent that the uprights (orthostats) do not stand perfectly vertically. They are gently tilted toward the interior with an average angle of 85.2 ± 1.6° (left side)–84.0 ± 2.0° (right side) with regard to the horizontal (i.e., the floor). This causes the space inside the dolmen to have a trapezoidal section.
As well as leaning inward, the orthostats also lean sideways against each other, with angles of 80°, 86°, and 88°, both on the right and left sides of the dolmen, with an average of 87.1 ± 2.4° (left side) and 88.0 ± 1.9° (right side). This is a key indicator to assess the order in which the stones were placed and, therefore, to infer how the monument was built.
The way the stones were placed provides numerous clues concerning the creative genius and early scientific engineering resourcefulness of the architects and engineers who designed and built Menga. The fact that they designed deep foundation sockets, in order that, when placed, one third of the uprights and pillars would stand underground, makes very plausible the use of counterweights to place them.
This technique, aimed at achieving a smooth and gradual tilting of the stones into the sockets, was crucial for two reasons.
1. This allowed for the placement of the stones with millimetric precision, both inside the sockets & with the adjacent stone.
2. It avoided the use of external descending ramps.
Several clues suggest that the uprights in Menga were dragged and placed from the inside out, not from the outside in, as previously thought.
Engineering reconstruction has conclusively shown that the placement of large stones is more efficient when the gravity point shifts gradually with the help of a moving counterweight. This procedure achieves a smoother tilting of the stone into its socket.
With this construction method, it was possible to achieve a near-perfect adjustment of the orthostats to each other. This explains the precise and regular angle at which they are positioned. The uprights created two strong “walls” to support the massive capstones. The trapezoidal orthostats “locked” with one another downward and upward forming a solid and lasting stone assemblage. No other monument built at that time shows that type of design.
Another striking element in the design on Menga is that a large proportion of the edifice was embedded into the bedrock. This feature, which is noted for the first time in the ~200-year history of research in this monument, has been recorded through a painstaking analysis of the plans and photographs (and topographic levels inferred from them) produced in the excavations of the universities of Málaga and Granada.
The uprights closest to the entrance of the dolmen (O-1 and O-23, under capstone C-1) are embedded to about 2.75 m in the bedrock. This means that one-third of these stones are underground. The uprights near to the back of the chamber (O-11 and O13, underneath C-5) are embedded even more deeply, around 3.20 m. This design was intended as a “box”; fully embedded in the bedrock, and therefore completely stable.
Another important element to understand the prolonged persistence of Menga is the durability of the tumular structure. The dolmen builders created an insulating mound that keeps the interior of the dolmen perfectly dry. This insulation is especially important because the highly porous rocks that compose the main support for the dolmen would suffer major weight changes and chemical and physical weathering due to water interaction.
The architects of the dolmen not only designed a building with pillars that could support the weight of these poorly consolidated rocks but also inferred the importance of considering the weight of the tumulus. This is deduced from the arch-shaped contour they gave to the upper side of capstone #5, which helps distribute vector forces from the center of the capstone toward the sides. Making Menga the first human-built stone structure functioning as a discharge arch.
The Dolmen of Menga is an extraordinary achievement of advanced engineering and construction, but it also represents a place of worship, a sacred place, to those who put forth so much care and effort to construct.
