If you're going to South America to climb a 6,000 meter peak you can use this map of 388 mountains to find suitable acclimatization peaks near your chosen climb.
They're broken down by height as follows:
- 5,000 - 5,200 meters: Yellow
- 5,200 - 5,400 meters: Orange
- 5,400 - 5,600 meters: Red
- 5,600 - 5,800 meters: Blue
- 5,800 - 6,000 meters: Purple
- Unknown: White
Acclimatization
Acclimatization is a natural physiological process. As you spend more time at higher altitudes, your body changes the ratio of white/red blood cells (or something like that), thus making you capable of operating at progressively higher altitudes.
Most achieve this by slowly going higher and higher each day. Typically the body is capable of acclimatizing at about 300 vertical meters per day. This varies person to person, but expect 250-400m.
"Climb high, sleep low" is the trusted maxim. In that it's the altitude you sleep at that really matters, but that going higher than that during the day - or exerting your self at that altitude is what will aid your acclimatization the most.
Alternatively you can take two other paths:
- Diamox / similar. Start taking it a day ahead of your climb starting. It comes with side effects, so many avoid this option completely.
- Altitude tents. If you have the money, sleep in an altitude tent for a couple of weeks before your trip, progressing the 'altitude' each night. This really isn't a cheap option.
But for most, shortcuts aren't what they climb mountains for. So that leaves you with two natural options:
- Climb various smaller peaks on the way to your main objective
- Do rotations on the main peak itself (eg Base camp to camp 1 and back, then to camp 1 and camp 2 but back to camp 1 to sleep, etc)
The first option I think is way more fun. You don't have to climb the same section twice (or more), and you get to see more places. Although if you really want to get to know a mountain - option two makes more sense.
Mountaineering in South America
With your acclimatzation out of the way, you can focus on climbing. Check out these starting points for each Country.