One of the most interesting aspects of Portuguese architecture is the use of tiles. There is a very long history of tile use, dating back to Roman times with the use of mosaic. Along with Spain, Portugal was a province of Rome for a long time. Julius Caesar cut his generalismo teeth prior to his caesarship in the wilds of Spain. Later, when Portugal and Spain was taken over by the Moors, tiles were used to cover floors, walls and ceilings or houses and mosques. After the Moors left, after losing a series of wars against Christian forces in the 1000-1200 period, tiles continued, adopting a more contemporary blue style. Many or most of the religious sites have blue tiles adorning walls, in and out, often with full on scenes from the life of Jesus. Essentially an entire painting, done over numerous tiles. It's quite common to see one of these tile scenes adorning houses as an ascent piece. Queen Mary from Fátima is probably the most common. She's everywhere.
More generically, tiles decorate houses and buildings, benches, streets.