Mrs Cat and I just got back from holiday in South America. We've been to Rio de Janeiro, Iguassu Falls, Mendoza, Santiago, Rapa Nui (Easter Island), Buenos Aires and São Paulo. It's been awesome, and I'd thoroughly recommend it to anyone.
Of all of those places, for me, the most moving was Rapa Nui. It's a tiny island with a long and turbulent history. The original Polynesian decendent inhabitants were master stone workers and built incredible monuments to their ancestors (which they ended up destroying later on). For me, the weirdest and most humbling place on the island is Rano Raraku - the quarry where the moai were made. Here there are dozens of still-standing moai, mostly partially buried. Apart from the onset of grass (and a tourist trail), it feels a lot like it's just a day off and that the workers will be back tomorrow to carry on carving.
Honestly, as the cliché goes, pictures don't do it justice. It's a hard place to get to, and expensive when you get there, but if you ever get a chance, it's a place well worth a visit.