See main text. Start at the Piedra Grande hut from which most of the route is visible. This is the same start as a few other routes and the only hut left on the mountain.
The first couple thousand feet of the climb is on a rough trail. The trail starts out near the hut, follows the aqueduct, then climbs further up the ravine. Although it begins well-marked, the trail becomes a network of winding social trails further up. At night this is confusing but climbers should be okay as long as they continue upward without doing something stupid like accidentally climbing the sarcofago.
Experiences transitioning to the glacier can vary depending on which of the paths was taken. In most cases simply stepping over from rock to snow/ice is all that is necessary. In the case of climbers who stayed on the very bottom of the ravine there might be some boulders and short stretches of low-moderate angle water ice to cross.
On the way down in daylight the trip is very easy.
From the start of the glacier the route is very straight-forward or should I say straight up. At about 17,500 ft the glacier steepens to about 40 degrees. A few hundred feet higher and your at the crater rim near the aguja de hielo or ice needle. Follow the rim to the right to the summit.
A frequent question concerning this route is regards to any crevasse danger.
Yes, there are crevasses. In my experience, and the experience of climbers I have personally talked to, nobody has seen a crevasse wider than a few fingers on this route. Reportedly people have managed to find a crevasse to fall into but details are vague. Perhaps decades ago there were dangerous crevasses. If you can provide any additional information please post it here.
Crampons and ice ax. This route is commonly done without standard glacier travel/rescue gear. Note that it can ice up and have fall potential. It is important to get information on current conditions because some climbers do decide to take a rope and a few screws and even use them.