Perito Moreno Glacier. Say the name to any Argentine and an image of a huge wall of ice immediately springs to mind. It's plastered all over ads for Patagonia, and for good reason - there aren't may more memorable things than 60 metres of ice rising right out of the water (that's the equivalent of a 15-storey building).
It's one of two non-receding glaciers left in the world (the other is on the Chilean side of the border), advancing about 2 metres a day (though about that much falls off the front, so it's just kind of sitting there). We saw a few spectacular breaks. They say it sounds like thunder, though it sounds more to me like a giant's bones breaking. We had a perfect day, too - the guide kept saying there are about 20 days like this in the year.
If you look closely, you can see the people on the top of the boat. Gives a bit of scale.