6 miles (10 km) from Skara Brae, grooved ware pottery was found at the Standing Stones of Stenness (originally a circle) which lie centrally in a close group of three major monuments. Maeshowe, the finest example of the passage grave type of chambered cairn (radiocarbon dated to before 2700 BC) lies just to the east. The Ring of Brodgar circle of standing stones is across a bridge immediately to the north. This circle was one of the first to be analysed by Professor Alexander Thom to establish the likely use of standing stones as astronomical observatories. Another Neolithic village has been found nearby at Barnhouse Settlement, and the inference is that these farming people were the builders and users of these mysterious structures. Like the standing stones at Callanish on Lewis and other standing stones across Scotland, these monuments form part of the Europe-wide Megalithic culture which also produced Stonehenge in Wiltshire and the stone rows at Carnac in Brittany. Further evidence can be found in Kilmartin Glen with its Stone Circles, Standing Stones and Rock Art The widespread connections of these people are shown by offerings imported from Cumbria and Wales and left on the sacred hilltop at Cairnpapple Hill, West Lothian, as early as 3500 BC. Bronze Age The cairns and megalithic monuments continued into the Bronze Age, though there was a decline in both the building of large new structures and the total area under cultivation. The Clava cairns and standing stones near Inverness show complex geometries and astronomical alignments, with smaller, perhaps individual, tombs instead of the communal Neolithic tombs. Mummies dating from 1600 to 1300 BC have been discovered at Cladh Hallan on South Uist. Hill forts were introduced, such as Eildon Hill near Melrose in the Scottish Borders, which goes back to around 1000 BC and which accommodated several hundred houses on a fortified hilltop. Excavation at Edinburgh Castle found late Bronze Age material from about 850 BC. Iron Age From around 700 BC and extending into Roman times, the Iron Age was an age of forts and defended farmsteads, which support the image of quarrelsome tribes and petty kingdoms recorded by the Romans. Evidence that at times occupants neglected the defences might suggest that symbolic power was as significant as warfare. Brythonic (or "Pritennic") Celtic culture and language spread into southern Scotland at some time after the 8th century BC, possibly through cultural