Stonehenge, Ireland

Stonehenge is a well-known stone monument found on a world heritage site in Salisbury Plain, Wiltshire, England. The site as is moderately large and contains many other structures from the Neolithic period and the Bronze Age. Stonehenge is contemplated as one of the mainly archaeologically rich sites in Europe, with many Neolithic and Bronze Age finds. It is also the site of one of the biggest Chalk grassland reversion projects in the world. Stonehenge has been occupied since around 8000BC with early work at Stonehenge beginning in 3000BC when an outer ditch and embankment were constructed, and standing timbers erected. From about 2500BC, Neolithic and Bronze age man started to bring Bluestones and Sarsen stones from Wales and the Marlborough Downs, it was completed in 1600BC. A nearby hill fort was built during the Iron Age, and there is evidence to suggest that the area was extensively settled by the Romans. The reason behind the structure still remains a mystery with many theories developed to explain the phenomenon.
More than nine hundred stone rings exist in the British Isles, and scholars guess that twice that number may originally have been built. Scholars usually group these types of megalithic structures as rings rather than circles, seeing as the rough proportions for the different shapes are 2/3 true circles, 1/6 flattened circles, 1/9 ellipses, and 1/18 eggs. Stonehenge, nevertheless, is roughly circular. It is difficult about precisely date the stone rings because of the scarcity of datable remains associated with them, but it is known that they were built during the Neolithic period. In southern England the Neolithic period dates from the development of the first farming districts around 4000 BC to the evolvement of bronze technology around 2000 BC, when the construction of the megalithic monuments was mostly over. Because of the limited nature of the archaeological record at the stone rings, attempts to explain the functions of the structures are often interpretive. Interpretations of the stone rings made in previous centuries tended to reflect the cultural biases of their times and were sometimes wildly imaginative. Only in the past few decades have truly comprehensive examinations of Stonehenge been conducted by archaeoastronomers such as John Michell, Robin Heath and John North. It is interesting to note that more than 40,000 megalithic sites have survived in the British Isles, this number exceeding the number of modern towns and villages, and yet only a small percentage of these have been thoroughly studied.
In the seventeenth century, well before the development of archaeological dating methods and accurate historical research, the antiquarian John Aubrey surmised that Stonehenge and other megalithic structures were constructed by the Druids. While this idea (and a collection of related fanciful notions) has become an unquestioned belief of popular culture from the seventeenth century to the present age, the Druids had nothing to do with the construction of the stone rings. The Celtic society, in which the Druid priesthood functioned, came into existence in Britain only after 300 BC; more than 1500 years after the last stone rings were constructed. Furthermore, little evidence suggests that the Druids, upon finding the stone rings positioned across the countryside, used them for ritual purposes. Druids are known to have conducted their ritual activities mostly in sacred forest groves. Therefore, a Druidic connection, in a construction sense, with the stone rings is inaccurate. Other seventeenth- and eighteenth-century visitors to the stone rings suggested that these monuments were constructed by the Romans, but this idea is even more lacking in historical possibility than the Druid theory because the Romans did not enter the British Isles until 43 AD, nearly 2000 years after the construction of the stone rings.
During the nineteenth and early twentieth centuries, prehistorians attributed Stonehenge and other stone rings to Egyptian and Mycenean travelers who were thought to have infused Europe with Bronze Age culture. With the development of Carbon-14 dating techniques, the infusion-diffusion conception of British Neolithic history was abandoned and the megalithic monuments of Britain (and Europe) were shown to predate those of the eastern Mediterranean, Egyptian, Mycenean, and Greek cultures.
While the Carbon-14 method provided approximate dates for the stone rings, it was of no use in explaining their function. During the past few decades the orthodox archaeological opinion generally assumed their function to be concerned with the ritual activities and territorial markings of various Neolithic chiefdoms. Research by scholars outside the orthodox bounds of the discipline of archaeology began to suggest an alternative use. In the 1950s and 1960s, the Oxford University engineer Professor Alexander Thom and the astronomer Gerald Hawkins pioneered the new field of archaeoastronomy - the study of the astronomies of ancient civilizations. Conducting precise theodolite surveys at numerous stone rings and other types of megalithic structures, Thom and Hawkins discovered many significant astronomical alignments among the stones. This evidence suggested that the stone rings were used as astronomical observatories. Moreover, the archaeoastronomers revealed the extraordinary mathematical sophistication and engineering abilities that the native British developed before either the Egyptian or Mesopotamian cultures. Two thousand years prior to Euclid's elucidation of the Pythagorean triangle theorems and at least 3000 years before the sixth century AD sage Arya Bhata had "discovered" the concept and value of Pi, the British megalithic builders were incorporating these mathematical understandings into their stone rings. Adding to the revolutionary findings and interpretations of Thom and Hawkins, studies by Aubrey Burl and Benjamin Ray have focused on the stone rings as astronomical observatories and also on their possible "magico-religious" uses.
Stonehenge, the most visited and well known of the British stone rings, is a composite structure built during three distinct periods. In Period I (radiocarbon-dated to 3100 BC), Stonehenge was a circular ditch with an internal bank. The circle, 320 feet in diameter, had a single entrance, 56 mysterious holes around its perimeter (with remains in them of human cremations), and a wooden sanctuary in the middle. The circle was aligned with the midsummer sunrise, the midwinter sunset, and the most southerly rising and northerly setting of the moon. Period II (2150 BC) saw the replacement of the wooden sanctuary with two circles of ‘bluestones’ (dolerite stone with a bluish tint), the widening of the entrance, the construction of an entrance avenue marked by parallel ditches aligned to the midsummer sunrise, and the erection, outside the circle, of the thirty-five ton ‘Heel Stone’. The eighty bluestones, some weighing as much as four tons, were transported from the Prescelly Mountains in Wales, 240 miles away.