Why would Ancient Aliens build structures out of stone, instead of space age plastics and metal alloys?

I am a firm believer that some of the megalithic structures could only have been built with some kind of unknown technology.

But what I always get stuck on is, why use stone? If we became advanced enough to travel to other planets, would we use stone to build our bases? hell no. We would use space age materials.

Why would an advanced alien race use stone ?

Submitted January 22, 2017 at 02:54PM by Conspiranut http://ift.tt/2k59xoL