Azulejo is a form of Portuguese painted tin-glazed ceramic tilework. It covers churches, palaces, ordinary houses, schools, restaurants, and even subway stations. They are not only used as an ornamental art form, but also had a specific functional capacity like temperature control in homes. They still constitute a major aspect of Portuguese architecture as they are applied on walls, floors and even ceilings. They are in other words EVERYWHERE and became an obsession as we were walking around Lisbon.
Full set here.