Rio de Janiero provides a great chance to see the Christ the Redeemer statue. It is very crowded and we had a downpour waiting to return to the bottom of the mountain. We wound up having to stand for the 25 minutes it took to ride down a very steep incline. For 2 people over 75 this was difficult if not dangerous. This was during carnival time and we found the city to be dirty and crowded.
Bueno Aires is a lovely city. This is one place and with a few more where H.Stern , a jeweler, provides free shuttle to town. By all means use it unless you are on a tour.