The history of Northamptonshire spans the same period as English history. Prehistory Much of Northamptonshire's countryside appears to have remained somewhat intractable with regards to early human occupation, resulting in an apparently sparse population and relatively few finds from the Palaeolithic, Mesolithic and Neolithic periods. In about 500 BC the Iron Age was introduced into the area by a continental people in the form of the Hallstatt culture, and over the next century a series of hill-forts were constructed at Arbury Camp, Rainsborough camp, Borough Hill, Castle Dykes, Guilsborough, Irthlingborough, and most notably of all, Hunsbury Hill. There are two more possible hill-forts at Arbury Hill (Badby) and Thenford. Roman occupation In the 1st century BC, most of what later became Northamptonshire became part of the territory of the Catuvellauni, a Belgic tribe, the Northamptonshire area forming their most northerly possession. The Catuvellauni were in turn conquered by the Romans in 43 AD. The Roman road of Watling Street passed through the county, and an important Roman settlement, Lactodorum, stood on the site of modern-day Towcester. There were other Roman settlements at Northampton, Kettering and along the Nene Valley near Raunds. A large fort was built at Longthorpe. Anglo-Saxons After the Romans left, the area eventually became part of the Anglo-Saxon kingdom of Mercia, and Northampton functioned as an administrative centre. The Mercians converted to Christianity in 654 AD with the death of the pagan king Penda. At some time in the 7th century the district which is now Northamptonshire suffered a simultaneous invasion by the West Saxons from the south and the Anglian tribes from the north. Relics discovered in the county testify to a mingling of people, at the same time showing that West Saxon influence never spread farther north than a line from Daventry to Warwick, and with the extension of the Mercian kingdom under Penda and the conversion of the midland districts ceased altogether. Abbeys at Medehamstede (now Peterborough) and Pipewell were begun by Peada in 655, and at about the same time foundations were established at Peakirk, Weedon Beck, Castor and Oundle. From about 889 the area was conquered by the Danes (as at one point almost all of England was, except for Athelney marsh in Somerset) and became part of the Danelaw – with Watling Street serving as the boundary – until being recaptured by the English under the Wessex king Edward the Elder,