English: Vertiginous streets in Ouro Preto, Minas Gerais state, Brazil. July 2006. Ouro Preto is the jewel in the crown of Minas Gerais's colonial towns. It was Brazil's wealthiest city during the 18th-century gold boom, and in 1931 the city fathers issued an edict that the town's architectural character had to be preserved -- i.e., no modern constructions would be permitted. Today it must stand as the most extensive colonial complex in the Americas, with the possible exception of the old city of Cartagena de Indias in Colombia (the most beautiful square mile on the face of the earth). Restoration continues apace, and far from feeling like a museum, Ouro Preto is also a major university town, with a youthful and vibrant ambience.