Street vendors play their trade from stalls in the tianguis as well as at non-officially controlled concentrations around metro stations and hospitals; at plazas comerciales, where vendors of a certain "theme" (e.g. stationery) are housed; originally these were organized to accommodate vendors formerly selling on the street; or simply from improvised stalls on a city sidewalk. In addition, food and goods are sold from people walking with baskets, pushing carts, from bicycles or the backs of trucks, or simply from a tarp or cloth laid on the ground.