"Azulejo" is a word used in Spain and Portugal to designate a glazed tile: a terracotta tile covered with an opaque glazing. In these two countries, azulejos have been frequently used since the 13th century to cover and decorate walls, fountains, pavements, ceilings, vaults, baths, or fireplaces.The first known glazed tiles come from Egypt and Mesopotamia. In 2620 BC, Pharaoh Djoser, founder of the 3rd dynasty, built in Saqqarah by his architect Imhotep a pyramid whose galleries leading to the funerary chamber are covered by green glazed tiles with yellow lines imitating papyrus stems. Glaze, sometimes called "enamel", which is a thin glass coating rendered opaque, is therefore an ancient discovery. However, in antiquity, this technique was exclusively oriental, and in fact, was subsequently lost: the Greco-Roman world did not of know it. To decorate surfaces, Greeks and Romans developed several techniques such as painting on wet plaster ("fresco"), or stucco, or mosaic.