If you are anticipating going to Bariloche during your trip to Argentina, Nahuel Huapi National Park and lake (which is part of the Route of Seven Lakes) are unmissable.
At the foot of Cerro Tronador, near Pampa Linda, Castaño Overo Glacier is one of the 7 glaciers in the natural reserve. If you have seen Perito Moreno, near Calafate, then you are not going to be very impressed by this glacier. But, you will be delighted by the beauty of Nahuel Huapi National Park. It's easy to understand why it's one of the most visited national parks in the country!
I didn't go trekking to explore Castaño Overo a bit more because I was on a lazy holiday with friends, but this day long trek doesn't require you to be an experienced climber. Sport or choclate? It's your choice!