Porto held as well endless churches that are decorated with the finest tiles in white and blue, and here and there a touch of yellow, the famous "azulejos". They not only adorn the walls of churches and monasteries but also of simple houses and fountains. They often portray scenes from the country's history or just serve as street name signs or house numbers. The word "azulejo" comes from the Arabic word "az-zulayj", meaning polished stone. In the 18th century, no other European country produced as many tiles for such a variety of purposes and in so many different designs than Portugal. Today, they are still a crucial part of the architecture of Porto. The Church "Igreja de Santo Ildefonso," has an imposing facade, clad in blue and white "azulejos," one of the nicest of Porto.