Tiwanaku (Tiahuanaco) is a complex of buildings, temples and a pyramid from pre-Inca times and is therefore Bolivia's most important archeological site.
The site consists of two museums and the archeological grounds with the buildings. One museum hosts mostly ceramic artifacts and the other one only hosted one sculpture by the time I visited it (June 2008). More artifacts and sculptures will be brought from the archeological site to the museums in the near future for preservation.
The archeological site has a piramide that covers more square meters than the one from Geops in Egypt, but is less tall. Total excavation is to be done in about 7 years. Interesting are the way the bricks are placed on the buildings (just like the Inca's used to do it later on), the ear-shaped loudspeaker, the interesting and very detailed carving on the sculptures and the faces on the wall of the Semi-subterranean Temple.