Some time later, minor changes took place around the outer parts of the monument. A circular ditch was dug around the Heel Stone and its companion stone was removed. Three stones were raised in a line across the entrance causeway, the Slaughter Stone, now fallen, being the sole survivor. Two of the Station Stones were also surrounded by low, ditched mounds, known as the North and South Barrows.

What spectacularly changed Stonehenge, however, was the arrival, shaping and raising of the 75 sarsens that go to form the outer circle and the horseshoe of massive trilithons. This seems to have happened in about 2500 BC, but over what length of time this major construction took place is unknown. There is also a lack of archaeological evidence to show in which order the two main structures were built. Logic suggests, that the horseshoe of trilithons was built first, or at least before the outer circle was finished – whether it ever was completed is uncertain. Much of it is now missing and there is one upright on its southern side that would never have reached the required height to support a lintel. Perhaps the supply of suitable stones simply ran out before the structure was completed. Finished or not, in its original form the outer circle must have been an extremely elegant structure. The gently curved lintels were beautifully shaped and jointed and the upper surface of the stone ring that they formed was almost exactly level, even though Stonehenge is built on a slope.




Equally elegant and even more massive were the five sarsen trilithons, graduated in size from the shortest that lay at the open end of the horseshoe to the tallest, the Great Trilithon, that stood facing the enclosure entrance. This horseshoe re-emphasized the alignment of the whole temple, originally established by the position of the entrance into the earthwork enclosure. It is possible that the bluestones still stood in their Q and R Hole settings or indeed that they were raised at the same time as these great sarsen structures.




The completion of the sarsen circle and trilithon horseshoe marked the end of a massive undertaking for the builders of Stonehenge. Their engineering on a monumental scale had created the most iconic prehistoric structure in the world.