In the Middle Stone Age (Mesolithic), people were hunter-gatherers. They would arrive at a valley, plunder it for the fruit and nuts they could find, catch and eat the animals, and then move on to the next valley. If someone died during this time, there was little they could do to express their respect for the body other than, perhaps, put it in a cave and cover it with stones.

The discovery of herding and agriculture brought in the New Stone Age, or Neolithic. Now people settled permanently in one place. They knew where their next meal was coming from; and they could treat their dead with proper respect. They had two choices: to place the dead body in an individual grave as we do, or to build one or more communal tombs of stone ('dolmens') that would house the bodies of the members of an entire family, or even clan. Surprisingly, throughout Europe and the Mediterranean, the Neolithic peoples all opted to build dolmens.

When archaeologists study dolmens, nearly every judgement they make is qualitative: the type of pottery, the clothing, the bones that are found. But there is one aspect of a dolmen that is quantitative: the direction in which it faces. A dolmen must have an entrance that can be opened to allow the deposition of the body of someone who has newly died, and so a dolmen has an orientation. Conventionally, a dolmen that faces north has orientation 0o, one that faces east 90o, and so on.

Nearly all dolmens are of one of two forms. The majority are 'megalithic', made up of a small number of large stone slabs. Typically there is a vertical backstone, two or three vertical stones to each side, a vertical entrance stone with a hole cut in it, and one or more horizontal slabs to form the roof. At Montefrío, midway between Antequera and Granada, there is a site with some 41 megalithic dolmens.

Other tombs are built with a large number of small stones, and these are spoken of 'tholos', a Greek word used to describe similar tombs found in Greece. A typical tholos has a circle of stones at ground level. On top of these is placed another circle of stones, but this time the diameter of the circle is very slightly smaller. And on top of these is placed another circle of stones, and again the diameter of the circle is slightly smaller. And so on. Because the diameters get smaller and smaller, the roof that is being created slopes upwards and inwards, and the result is a building in the shape of a beehive. At Los Millares, near Almería, there are some 48 tholos tombs.

Very occasionally a large dolmen was built in isolation, but the great majority were built in groups. And because each dolmen has an orientation, we can measure the orientations of all the dolmens of a group and then consider the numbers that we have assembled. It is theoretically possible for the collection to be of random numbers, but in fact this is never the case: the builders always followed a custom when chosing the orientation for a new dolmen. Perhaps we can understand the motivation underlying this custom. It turns out that in Iberia very many dolmens, whether megalithic or tholos, faced directions in which the sun rises at some time of year.

In Iberia, apart from the very rare dolmen built in isolation, we find numerous collections of dolmens all of the same type, megalithic in Montefrío, tholos in Los Millares. That is, except in Antequera. There we have one gigantic megalithic dolmen (Menga), one gigantic tholos (El Romeral), and one gigantic dolmen of very rare construction (Viera). To have in a single site one dolmen each of three types occurs nowhere else; and the scale of the monuments is nowhere surpassed.

Because we have only one dolmen of each type, we do not have a collection of orientations that might reveal the motives in the minds of the builders, and so there is a limit to what we can say in explanation of the orientations. Viera faces roughly east like so many dolmens, in the range of sunrise. El Romeral faces south-southwest, an unusual orientation for an Iberian dolmen, but one common in the south of France. But Menga is special, for it faces northeast, in a direction where the sun is never seen. This orientation is wholly unique. But when we look out from the interior of Menga the reason for the orientation is obvious: it faces the extraordinary mountain of La Peña de los Enamorados, which is well-known as a prehistoric site and which has the bizarre and unsettling shape of a sleeping giant. Menga may well be the only dolmen in Iberia whose orientation has a terrestrial, rather than celestial, motivation.