The ancient Bolivian site aligned with the winter solstice is Tiwanaku, particularly through the astronomical orientation of its Kalasasaya complex.
Tiwanaku was a major pre-Columbian ceremonial and political center in the Andes, located near Lake Titicaca in western Bolivia. Its builders incorporated observations of the Sun, Moon, stars, and Milky Way into the planning of important monuments. Kalasasaya was arranged to frame sunrise at significant points in the annual solar cycle, including the equinoxes and solstices.
At the winter solstice in the Southern Hemisphere, which occurs around June 20 or 21, the Sun follows its lowest and shortest apparent daily path. The solstice alignment therefore helped mark the seasonal turning point, while the opposite summer-solstice alignment occurred around December 21 or 22. Tiwanaku's architecture was not simply a calendar in stone, however: scholars still debate the precise ritual and practical purposes of these orientations.
A common mix-up is Chankillo, an important solar observatory in Peru. It is also famous for solstice alignments, but it is not in Bolivia. Tiwanaku was designated a UNESCO World Heritage Site in 2000.