Quito, Ecuador
We were only in Quito for four days but wished for a longer stay. Quito is a vibrant city, and, at 2,800 meters high, the second highest capital city in the world (after La Paz, Bolivia). We had gradually come up to that altitude, after Loja (2,000 meters) for 2 days, and Cuenca (2,500 meters) for over a week. We did notice the altitude, especially going up to the statue of the Virgin, with some shortness of breath.
Quito seems to be more of a real city, after spending time in Cuenca. It has several major city centers; we stayed in the Old City and also in La Mariscal. After a day, we were pretty comfortable with the bus system, and had taken some walking tours and seen several museums.