Best views of the mountains and three lakes "Tres Lagunas".
Touching the void
There is an alternative shorter start saving a day and half by going by bus further to Pocpa and walking by road through Pallca to Matacancha camp site.
At the time we had to hire a cab for the last part, but now the bus goes right from Lima to Llamac (1.5 h, 15 soles) from Chiquián.
Cabs in Peru were ubiquituous and cheap.
Descent to Catajambo
The first night is already above 4000, so you have to be properly acclimatized before.
There is plenty of water on the trek, but it must be treated by UV light or chemicals. We used a treatment based on silver (Sanosil DDW) that does not affect a taste much.
There is also a slightly shorter alternative as a circuit with a bit more climbing.
Map of Area