"the walls of Mexican houses that have been plastered by hand"
Mexico is one of the many places in which houses have been constructed of adobe, an extremely durable material made by combining sand, water, clay and some form of organic material, such as straw or manure. This substance was originally built up in wet layers until bricks were introduced by the Spanish in the 16th
century. These are left to dry in the sun before being used to construct the walls. When the structure is complete, mud-plaster is applied to the exterior.