Guallatiri is on of the three triplets (Quimsachatas in Aymara). It is the highest of the three and reaches 6070m altitude. It is entirely on the Chilean side of the boarder and is therefore climbed while visiting Chile. 

 

It can be climbed within 2 days from Putre. The first day you'll rive up along the Khota Khotani lagoons and Chungara lake until you reach the Frontier. From there you'll drive along a dirt road in Lauca National Park to reach the base camp at 5200m altitude. The night be cold, but the views on Parinacota and Pomerape are priceless. 

 

The ascent will take you through snow/ice fields and end next to a powerfull fumarole close to the summit.