As to the age of the site, it's about 15
00 years old -- not 17,
000 as you see in more credulous, paranormal-friendly articles.
Determining the age of the Pumapunku complex has been a focus of researchers since the discovery of the Tiwanaku site. As noted by Andean specialist, Binghamton University Anthropology professor W. H. Isbell, a radiocarbon date was obtained by Vranich from lowermost and oldest layer of mound fill forming the Pumapunku. This layer was deposited during the first of three construction epochs and dates the initial construction of the Pumapunku at 1510 ±25 B.P. C14 (AD 440; calibrated, AD 536–600). Since the radiocarbon date came from the lowermost and oldest layer of mound fill underlying the andesite and sandstone stonework, the stonework must have been constructed sometime after 1510 ±25 B.P. C14. The excavation trenches of Vranich show that the clay, sand, and gravel fill of the Pumapunku complex lies directly on the sterile middle Pleistocene sediments. These excavation trenches also demonstrated the lack of any pre-Andean Middle Horizon cultural deposits within the area of the Tiwanaku Site adjacent to the Pumapunku complex.
--summarized from:
Isbell, William H. (2004), "Palaces and Politics in the Andean Middle Horizon", in Evans, Susan Toby; Pillsbury, Joanne, Palaces of the Ancient New World, Washington, D.C.: Dumbarton Oaks Research Library and Collection, pp. 191–246, ISBN 0-88402-300-1,
http://www.doaks.org/publications/doaks_online_publications/isbn_0-88402-300-1.pdf, retrieved 2010-04-26
Vranich, A., 1999, Interpreting the Meaning of Ritual Spaces: The Temple Complex of Pumapunku, Tiwanaku, Bolivia. Doctoral Dissertation, The University of Pennsylvania.