A shanty town or squatter area is a settlement of improvised housing, called shanties or shacks, made of plywood, corrugated metal, sheets of plastic, and cardboard boxes. Such settlements are usually found on the periphery of cities, in public parks, or near railroad tracks, rivers, lagoons or city trash dump sites. Sometimes called a squatter, informal or spontaneous settlement, a typical shanty town often lacks proper sanitation, safe water supply, electricity, hygienic streets, or other basic human necessities.