Plastering the exterior of Porto's 18th-century Carmo church is a blaze of blue and white azulejos (tiles), and the striking façade is one of the most instantly recognized in the city. The immense panel is a real head turner, but the splendid gilt carvings that decorate the interior are equally appealing. In fact, the elegant golden-brushed woodwork is among the finest examples of Portuguese Rococo. The neighboring Igreja das Carmelitas is less of an eye-opener. Incredibly, dividing both is a house, built to comply with an ancient law that stipulated that no two churches were to share the same wall. Many believe this to be the narrowest private residence in the country, although it's been unoccupied for nearly 30 years. A whimsical anomaly, the one-metre wide abode makes for an interesting snapshot squeezed as it is between two granite monoliths.