Tiles (called azulejos) are everywhere in Portugal. They decorate everything from walls of churches and monasteries, to palaces, ordinary houses, park seats, fountains, shops, and railway stations. They often portray scenes from the history of the country, show its most ravishing sights, or simply serve as street signs, nameplates, or house numbers. Although they are not a Portuguese invention (the use of glazed tiles began in Egypt), they have been used more imaginatively and consistently in Portugal than in any other nation. They became an art form, and by the 18th century no other European country was producing as many tiles for such a variety of purposes and in so many different designs. Today, they still remain a very important part of the country's architecture. After the Gothic period, most large buildings had extensive areas of flat plaster on their interior walls, which needed some form of decoration. These empty architectural spaces produced the art of the fresco in Italy, and in Portugal, the art of the azulejo.