Chacaltaya, the former highest ski resort in the world, is a very easy climb.
We took a jeep up to the (remaining of) the old ski lodge, at 5,300 meters. This ride takes about 1,5h from La Paz and almost all tour agencies in La Paz offer this daytrip, usually in combination with the Valle de la Luna which is worth a visit.
From this trailhead, you walk up to the first peak, then down, and up again to the summit which is at 5,421 meters (17,785 ft). This walk took us 45 minutes, and we are beginning mountaineers with little experience. It is important to be well acclimatised though, which we achieved being in the high part of Bolivia (3,000-5,000) meters for ten days.
Chacaltaya used to have a big glacier, but unfortunately this melted away years ago. Today we were surprised, as was our guide, to see a fair amount of snow on the mountain. This made it slightly more difficult but more beautiful too. Along the way you have a great view of Huayna Potosi, if the sky is clear.
We booked through Travel Tracks and paid BOL 100 each for the whole day. We can really recommend this agency. Our guide, Nelson, was a nice guy and really knowledgeable.