Throughout much of the hills and habitable mountainous ranges, most settlements consist of loosely clustered households surrounded by agricultural land. Households usually group on a hilltop or hillside and near a river or spring. They are connected by footpaths that often converge around a large pipal or banyan tree, which is surrounded by a stone platform and seating structure ( chautara ) that serves as a resting place for travelers and a meeting place for informal or village-council social gatherings. Most hamlets consist of a few clans ( thar ) of a particular group (e.g., Magar, Gurung) and often one or more households of artisan castes (e.g., metalworkers) . There are also more densely compact settlements among the Brahmans and Chhetris, Sherpa, Newari, and others that may consist of over fifty households as well as small shops and schools. Throughout the hills there are a number of large towns consisting of several hundred or a few thousand people, especially where there is an important temple or monastery, a marketplace, a motorable road, or an administrative center. The Newari have typically lived in cities or large towns that each form a commercial, social, and ritual center surrounded by their terraced fields. Their settlements vary in size from large villages to the former city-states of Patan, Kathmandu, and Bhaktapur in the Kathmandu Valley. However, the most common houses in the middle hills are two-story, mud-brick houses with thatch—or, recently, tin—roofs. The bottom of each house is painted in red-clay ocher and the top half is whitewashed. The floor is cleaned regularly with a newly applied mixture of wet cow dung and clay. The kitchen must be kept pure, so it is often located on the second floor of the house in order to avoid the pollution of stray animals that might wander into it. Most houses have a veranda and a courtyard where people socialize and work on weaving, corn husking, and other chores. In the northern, mountainous regions of Nepal, such as among the Sherpa or people of Dolpo, houses are made of stone and wood. In the southern, lowland region of the country houses are made of bamboo matting, plastered with mud and cow dung, and covered with a thatch roof. In Newari towns and cities, houses are more elaborate three-story dwellings of stone or baked brick with tin or slate roofs, and they may have carved windows and courtyards in the middle of the house. Simplified versions of these houses are being made of cement or brick throughout the Kathmandu Valley to accommodate its current population boom.