Curitiba

Curitiba needs 2 days: the Botanical Garden, with its art nouveau-style iron-and-glass greenhouse -the city's most photographed image-, on one, and the Ópera de Arame, a circular theater with a tubular metal structure inside a repurposed quarry, on the other. April-October brings the mildest weather. It's mid-priced by Brazilian standards. It's a world pioneer in sustainable urban planning: its dedicated-lane articulated bus system, devised in the 1970s, became the model for bus rapid transit in dozens of cities worldwide, and it usually tops quality-of-life rankings among Brazilian state capitals.