I think Rio is one of the world's prettiest locals for a major city. As beautiful a setting as the fjords of Norway but with better bikini beaches.
The dense granitoid basement rocks make for dramatic landforms and steep cliffs with unofficial slums, or favelas, clinging to the slopes.
Here is a bit of free-ride urban trials that had to be done with the permission & under the protection of the favela's drug lord ( the city police don't even dare to go there).
Enjoy!