I'll be in Brazil in June. I have a 12hr (0800-2000) layover in Sao Paulo. Anything that would be worth seeing/doing for 8hrs and not miss my flight? I also have 2-3 free days in Rio. Any must see's/do's besides going up Corcovado Mountain and Sugar Loaf Mountain, Iguassu Falls (all are already on my itinerary)? Is it safe to walk alone at night/dark in Rio and Sao Paulo?