There are many underground water conduits @ Tiawanaku. Some undiscovered, and some have been studied, and they do deserve more attention. (IIRC, a Mr. Bennett did some work on this in 1934-35, but his Paper is also now unavailable....maybe try google. His and Protzen's Papers were once avail. on the Atlantis/Bolivia site at one time, but are now removed.)
There is a step-pyramid located @ Tiawanaku called the Akapana Pyramid. (I include Puma Punku as part of the Tia Temple Complex.)
The Pre Incas did their foundry work on-site and made the I-Cramps used to repair/secure the large stones. Unfortunately, very few exist now as the Spanish melted many of them down to make bells for their Missions.
I don't buy into the Machining 'Theory'...this is a Criss Dunn idea that the Ancient Alien Crowd has 'borrowed'.
From before the time the Spanish arrived in SA, the locals were pillaging stones from Tiawanaku, and this pillaging continues to this day. The damage they've caused shouldn't be underestimated.
The Spanish used gunpowder to damage/destroy the structures because they wanted to erase the locals' memories of their 'former' Gods, so they could convert them to Christianity. (Not to mention the many earthquakes, and at least one major flood that this site has endured.)
The Bolivian Govt. also removed large quantities of stones to build a Church in their Capital some yrs ago.
Believe it or not: The (Bolivian, IIRC) Military did use Tiawanaku as target practice, (using Hvy. Artillery) many yrs. ago....Post WW2, IIRC.
IMO, the strongest pc. of evidence there is for the direct connection is the description of Viracocha....he was a dark-haired man w/ a beard and blue eyes.
Campbell's Chamber roof blocks are Tura Limestone until proven otherwise.
THE Cartouche in Campbell's Chamber IS Authentic, as are ALL other RC's Glyphs, until proven otherwise.
"This Forgery 'theory' has more holes than a sieve basket."