THE Portuguese azulejo: The history of these glazed ceramic tiles forms as rich a mosaic as their designs.For the past five centuries, tiles have added color and dimension to Portuguese architecture: in grand old residences, on new blocks of modern apartment buildings, on firehouses, composing murals in churches, bordering highways, covering old manor houses, decorating commercial establishments, tucked away in castles, and paving streets. Tiles are everywhere. They invariably appear in formation, whether they compose ornate pictorial scenes of maidens and fruits or brilliantly colored geometric designs. The azulejo developed and traveled, given the unique geographics of the Portuguese. Portugal looks west over the Atlantic to the Americas. It reaches south to the Mediterranean and Africa; east to Iberia; and north to all of Europe. The possibilities for the developing azulejo artistry, of Arab origination, have known no bounds. Tiles spread from the European continent to islands in the middle of the Atlantic ocean. Azulejos have been prominent in such faraway lands as Brazil, an important former Portuguese territory. Foreign influences have made their way to Portugal: The Moors, the Italians, the Spaniards, and the Dutch all played roles in the various incarnations of the azulejos. The evolution of azulejos was in harmony with the development of Portuguese painting and sculpture. Flemish influences from the 15th century, for example, gave the tiles their deep coloring and detailed portraiture. By the 17th century, popular relief patterns that adorned buildings and gardens gave way to entire panels depicting religious and secular scenes. Eighteenth-century tiles formed compositions, such as broad landscapes, stories from the Bible, and hunting scenes. Well after the Industrial Revolution reached the azulejo with production techniques such as the copper mint, which facilitated repetition of a design, many artisans preferred and continued to paint tiles by hand. In fact, by the early 20th century, many tiled pictorials showed simple rural life. These offered strong statements about preserving the bucolic world in the midst of industrialization. Art Nouveau also emerged during this period, in bold contrast to the pictorials nostalgic for the simple life. Ornamental azulejos, rich in hue and complex in design, were popular. Raised designs added dimension and texture to fauna and flora. Art Deco artisans reacted with often severe, simple geometric and figurative designs. Later artists employed tiles in Cubist designs, perhaps one of the square tiles most natural decorative uses. Sant'Anna, one of the country's oldest tilemakers, celebrated its 250th birthday this year. Its Lisbon location, which includes a factory and store dating back to 1741, was unaffected by the 1755 earthquake. At the factory, visitors can see how the tiles are made. A plaster cast is formed, then the clay is applied, and put outdoors to dry. After drying, the clay is separated from the plaster, and artisans make final touches to the forms before placing them into a wood-fired kiln. Once the clay has cooled , it is glazed. Artists then outline their designs with charcoal dust. Finally, the tiles are painted before they are returned to the kiln for a second firing. Today, the tiles are both decorative and utilitarian. Among their contemporary uses, they provide beautiful facades for unsightly buildings under renovation and serve as roadside murals - a welcome relief to motorists. In Portugal's densely populated capital, in hundreds of newer villages that salt and pepper the countryside, along the quiet seaside and ocean towns, tiles transform space. In Lisbon's congested Alfama district, the oldest part of the city that remains after the great earthquake of 1755, the stone-paved streets are narrow and winding. Yet there is plenty of room for schoolyards and gardens, elegant walkways, and small specialty stores. White-washed cottages abut busy restaurants; men grill sardines under balconies where women hang clothing to dry. Cracked tiles on time-worn buildings offer the same visual relief they did centuries ago. An arduous climb through Alfama's slopes leads to St. George's Castle, a former stronghold of the Moorish governor that overlooks Lisbon and the river. Almost at the top, a small chapel contains paintings on glazed tiles depicting the capture of the city in the 12th century by Afonso Henriques, Portugal's first ruler. The works reveal what the environs looked like before the earthquake leveled most of the city about 500 years later. Even the most drab concrete structures, erected all over the country after World War I, are made elegant with a panel of azulejos. In the South, along the Mediterranean coast, where the Moorish-style white-stucco houses are a stark contrast to a brilliant blue sky, the sun-splashed tiles seem to dance off their surfaces. The muted greens, yellows, and browns are just as compelling as the cobalt blues and fiery reds. Here, as in all of Portugal, the azulejos are well worn with time, and remain to record it.