The eye-popping backdrop of the city demands some pretty strong and characterful architecture, and at periods in it's history, this has been delivered. 

Rio embraced modernism with gusto in the '60's, and much of what was built measures-up pretty well to today's view of good, enduring design. More recently (1996), the Museum of Contemporary Art was also built, across the water in Niteroi. 

It's a wonderful, fun, flying-saucer of a building - although unfortunately, built with a shoestring construction budget, it's already looking a bit worn at the edges.