A henge can be one of three related types of Neolithic earthwork. The essential characteristic of all three is that they feature a ring-shaped bank and ditch, with the ditch inside the bank. Because the internal ditches would have served defensive purposes poorly, henges are not considered to have been defensive constructions (cf. circular rampart).
The three henge types (figures in brackets indicate the approximate diameter of the central flat area) are:
Avebury (/ˈeɪvbəri/) is a Neolithic henge monument containing three stone circles, around the village of Avebury in Wiltshire, in south-west England. One of the best-known prehistoric sites in Britain, it contains the largest megalithic stone circle in the world. It is both a tourist attraction and a place of religious importance to contemporary pagans.
Constructed over several hundred years in the third millennium BC, during the Neolithic, or New Stone Age, the monument comprises a large henge (a bank and a ditch) with a large outer stone circle and two separate smaller stone circles situated inside the centre of the monument. Its original purpose is unknown, although archaeologists believe that it was most likely used for some form of ritual or ceremony. The Avebury monument is a part of a larger prehistoric landscape containing several older monuments nearby, including West Kennet Long Barrow, Windmill Hill and Silbury Hill.
A stone circle is a ring of megalithic standing stones. Most are found in Northwestern Europe – especially Stone circles in the British Isles and Brittany – and typically date from the Late Neolithic and Early Bronze Age, with most being built between 3300 and 2500 BC. The best known examples include those at the henge monument at Avebury, the Rollright Stones, Castlerigg, and elements within the ring of standing stones at Stonehenge. Scattered examples exist from other parts of Europe. Later, during the Iron Age, stone circles were built in southern Scandinavia.
The archetypical stone circle is an uncluttered enclosure, large enough to congregate inside, and composed of megalithic stones. Often similar structures are named 'stone circle', but these names are either historic, or incorrect. Examples of commonly misinterpreted stone circles are ring cairns, burial mounds, and kerb cairns. Although it is often assumed there are thousands of stone circles across the British Isles and Europe, such enclosures are actually very rare, and constitute a regional form of henge. Examples of true stone circles include Long Meg and Her Daughters in Cumbria, henges with inner stones such as Avebury in Wiltshire, and The Merry Maidens in Cornwall.
Newgrange (Irish: Sí an Bhrú) is a prehistoric monument in County Meath in Ireland, placed on a rise overlooking the River Boyne, eight kilometres (five miles) west of the town of Drogheda. It is an exceptionally grand passage tomb built during the Neolithic Period, around 3100 BC, making it older than Stonehenge and the Egyptian pyramids. Newgrange is the main monument in the Brú na Bóinne complex, a World Heritage Site that also includes the passage tombs of Knowth and Dowth, as well as other henges, burial mounds and standing stones.
Newgrange consists of a large circular mound with an inner stone passageway and cruciform chamber. Burnt and unburnt human bones, and possible grave goods or votive offerings, were found in this chamber. The monument has a striking façade made mostly of white quartz cobblestones, and it is ringed by engraved kerbstones. Many of the larger stones of Newgrange are covered in megalithic art. The mound is also ringed by a stone circle. Some of the material that makes up the monument came from as far as the Mournes and Wicklow Mountains. There is no agreement about its purpose, but it is believed it had religious significance. It is aligned so that the rising sun on the winter solstice shines through a "roofbox" above the entrance and floods the inner chamber. Several other passage tombs in Ireland are aligned with solstices and equinoxes, and Cairn G at Carrowkeel has a similar "roofbox". Newgrange shares similarities with some other Neolithic monuments in Western Europe; especially Gavrinis in Brittany, which has a similar preserved facing and large carved stones, Maeshowe in Orkney, with its large corbelled chamber, and Bryn Celli Ddu in Wales.
Silbury Hill is a prehistoric artificial chalk mound near Avebury in the English county of Wiltshire. It is part of the Stonehenge, Avebury and Associated Sites UNESCO World Heritage Site. At 39.3 metres (129 ft) high, the hill is the second tallest prehistoric man-made mound in Europe (after The Castle Hill in Udine, Italy) and one of the largest in the world; it is similar in volume to contemporary Egyptian pyramids. The site is in the care of English Heritage.
Silbury Hill is part of the complex of Neolithic monuments around Avebury, which includes the Avebury Ring and West Kennet Long Barrow. Its original purpose is still debated. Several other important Neolithic monuments in Wiltshire, including the large henges at Marden and Salisbury Plain (Stonehenge), may be culturally or functionally related to Avebury and Silbury.
Navan Fort (Old Irish: Emain Macha [ˈeβ̃ənʲ ˈβ̃axa]; Modern Irish: Eamhain Mhacha [ˌəunʲ ˈwaxə]) is an ancient ceremonial monument near Armagh, Northern Ireland. According to tradition it was one of the great royal sites of pre-Christian Gaelic Ireland and the capital of the Ulaidh. It is a large circular hilltop enclosure—marked by a bank and ditch—inside which is a circular mound and the remains of a ring barrow. Archeological investigations show that there were once buildings on the site, including a huge roundhouse-like structure that has been likened to a temple. In a ritual act, this timber structure was filled with stones, deliberately burnt down and then covered with earth to create the mound which stands today. It is believed that Navan was a pagan ceremonial site and was regarded as a sacred space. It features prominently in Irish mythology, especially in the tales of the Ulster Cycle. According to the Oxford Dictionary of Celtic Mythology, "the [Eamhain Mhacha] of myth and legend is a far grander and mysterious place than archeological excavation supports".
Navan Fort is the heart of the larger 'Navan complex', which also includes the ancient sites of Haughey's Fort (an earlier hilltop enclosure), the King's Stables (a manmade ritual pool) and Loughnashade (a natural lake that has yielded votive offerings).