Temple of Kalasasaya dates back to 200 BC - 200 AC or even 2000 BC. Total area of the temple is 1.47 ha with 126x117 meters sides. Most of the structure lies below ground level and can be reach my 6 step staircase, created from a single piece of stone. There are 7 partly underground rooms on each side of the temple.
Kalasasaya was used as a ceremonial center for astronomical observations allowing to define up to day on any date of the 365-day year. On fall and spring equinoxes (21 March and 21 September respectively) the light of Sun shined through the main entrance gate thus making us believe that Tiwanaku civilization known calendar and astronomy well.