How was it even possible to build this back then?

It is described as a massive megalithic mountain deep in the jungles.  It sounds like a fiction story but this place and structures really exists.  It is hard to figure out how a civilization during that time period would have had the tools to build this:

Located in the high Bolivian jungle, Samaipata is a unique ancient megalithic site whose creators are as of yet unknown…

It was occupied in the 14th century by the Inca, who made it a provincial capital. The walls in the foreground were created by the Inca.

This place is very mysterious and it may have been built in around 300 AD but they don’t know for sure.

Here is more information on this region from wikipedia:

It is not actually a military fortification, but it is generally considered a pre-Columbian religious site, built by the Chané people, a pre-Inca culture of Arawak origin.^[2] There are also ruins of an Inca city built near the temple; the city was built during the Inca expansion to the southeast. Both Incas and Chanes suffered several raids from Guarani warriors who invaded the region from time to time. Eventually, the Guarani warriors conquered the plains and valleys of Santa Cruz and destroyed Samaipata. The Guaranis dominated the region well into the Spanish colonial period.^[2]

What do you think?  Was this made by the Chane people or perhaps it was in part made by another culture or civilization?

Feel free to comment with your ideas.

thanks to hiddenincatours.com for the great info