This mountain is located just outside Cuzco. Some sources list its height as 4842 m. It is visible from certain sections in town. The peak is not major by Andean standards, but it is prominent nevertheless. I beleive it is the closest peak of its size to Cuzco. After doing some research, I found a little bit about Pachatusan. The name Pachatusan means "one that sustains the Earth" in the Quechua language. This mountain has some spiritual significance to the local people as it overlooks the Sacred Valley of the Incas and has commanding views in other directions. Ausangate (6400 m) can be seen from the top. We did not see other climbers on the montain, but we did see local villagers pretty close to the top. The easiest route would probably be Class 2. We did not take the easiest route on the way up and ended up bushwacking through some very thorny bushes and had to do some scrambling up higher. To get to the easiest route, hang left on a fairly prominent trail off the Inca trail before it ends. You will walk through some fields, then pass a village. We took this route on our way down. Basically, once you see the summit, it is up to you how to get up there as there are multiple trails that get you to the upper slopes. Once you are there, it is pretty much a Class 2/3 scramble.
From Cuzco, take Road #3 east past the village of Sayalla (10-12 miles), then follow signs to the archaelogical site of Tipon (3500 m). The road becomes rougher as you climb to the site. You will pass some villages along the way. The poverty jumps out at you as you go. Park at the site, the proceed past the gate on the Inca Trail. The mountain comes into view in roughly three hours give or take depending on which route you take. Keep in mind that some bushwacking may be required below treeline depending on the route that you take.
No permits, but you will have to pay the entrance fee to Tipon (5 sol).
The best time is the dry season - May to September. Snow may cover the upper slopes out of season.
I don't think there are any camping restrictions. There is a lake at about 4100 m which will make a nice campsite.