Palácio do Planalto Brasília

The Palácio do Planalto, where Brazil's president works, is another Niemeyer design that's worth seeing inside and out. From the curved lines of the exterior to the lustrous columns and sweeping curved ramp inside, it's one of the best examples of architectural modernism in the world. The tour even lets you peek into the president's office. There is a ceremonial changing of the guard outside the gates every hour on weekends and every two hours during the week.