the vale uncovered the remains of a large Anglo Saxon settlement. The vale is rich in the remains of the English medieval period, between the 11th and 15th centuries. There are castles, such as those at Helmsley and Pickering, as well as fortified manor houses and churches of the period. There is also a notable example of medieval strip fields at Middleton. In the 17th and 18th centuries wealthy landowners created fine buildings and estates such as those at Wykeham Abbey, Nunnington Hall and Ebberston Hall. The settlement pattern of the Vale of Pickering is striking. There are two types of settlement, both relating to the topography. The first group is the villages and towns on the northern and southern fringes of the area. These settlements were established in close proximity to each other on the approximate shoreline of the glacial lake. They were built along the spring line, where the underlying aquifers met less porous rocks. Many of the parishes associated with the settlements are linear running from the vale bottom upwards to the higher ground, meaning that the long narrow parishes each had an amount of different types of soil and elevation. The second type of settlement is on the valley floor. These are small more widely spaced villages in areas of rising ground. These villages result from the relatively late enclosure of the carr lands following their drainage at the beginning of the 19th century. Long narrow lanes and tracks with wide grass verges link these settlements and solid well managed hedges. Building materials vary from soft limestones and sandstones to harder gritstones. The steep slopes of the roofs suggests that the older buildings had thatch coverings but these have been mostly replaced by red pantiles. Economy The market towns of Helmsley, Kirkbymoorside, Pickering and Malton are the largest centres of population in the Ryedale District with about half of the population living there. The eastern part of the area is dominated by the influence of Scarborough. Each of the market towns within the Ryedale District has areas set aside for industrial use and small firms engaged in light industry and the service industries occupy these. The largest employer in the district is the Malton Bacon Factory, employing more than 2,000 people. Other businesses generally employ less than 25 people. In the Scarborough Borough area of the Vale of Pickering a small industrial estate is located at