Leicester is a city and unitary authority area in the East Midlands of England, and the county town of Leicestershire. The city lies on the River Soar and at the edge of the National Forest.In the 2011 census, the population of the Leicester unitary authority was 330,000, the highest in the region, whilst 509,000 people lived in the wider Leicester Urban Area, making Leicester the tenth largest city in the United Kingdom and England's eleventh largest urban area. It has the second largest urban area in the East Midlands region. Eurostat's Larger Urban Zone listed the population of Leicester LUZ at 806,100 people as of 2009. According to the 2011 census Leicester had the largest proportion of people aged 19-and-under in the East Midlands with 27 per cent."Unlike almost every other city in the UK, Leicester has retained a remarkable record of its past in buildings that still stand today". Ancient Roman pavements and baths remain in Leicester from its early settlement as Ratae Corieltauvorum, a Roman military outpost in a region inhabited by the Celtic Corieltauvi tribe. Following the demise of Roman society the early medieval Ratae Corieltauvorum is shrouded in obscurity, but when the settlement was captured by the Danes it became one of five fortified towns important to the Danelaw. The name "Leicester" is thought to derive from the words castra of the "Ligore", meaning camp of the dwellers on the (river) Legro. Leicester appears in the Domesday Book as "Ledecestre". Leicester continued to grow throughout the Early Modern period as a market town, although it was the Industrial Revolution that facilitated a process of rapid unplanned urbanisation in the area.