I’ve been to Rio de Janeiro, Brazil, and it’s pretty much cool. There’s monuments to visit, including the Christ, and the beach, the heat.. Everything that makes that’s a good place ! Though, there’s much violence, and as a tourist, you may be careful. I suggest you to buy a South America (or borrow at a library) guide. That should help you! :)

not in any particular order …

Machu Picchu and surrounds (Cusco, Lake Titicaca etc)

Patagonia specifically Torres del Paine National Park, and the Perito Moreno glacier)

the Lake District of Chile

Iguazu falls

Rio de Janeiro

Salvador, Brazil

Amazon (I went to it in Brazil, but I would recommend somewhere else like the manu National Park)

Buenos Aires

And a few places I haven’t been to but looked great —

The Galapagos Islands

Colca Canyon

I spent three months travelling around South America and in all honesty, it is a bit much to try to cover this range of places in that length of time. You will have a much less stressed trip if you try to focus it down a bit more. you also get to see more than just the obvious tourist stuff if you spend longer in a single place.