image credit; ESO
Neanderthals appear to have arranged a bunch of stalagmites in circles about 170,000 years ago.
Before cars, airplanes, computers and so on, the high technology of the day tended to be architecture. Another interesting technology was boats. I often like to say that the first architecture were temples for pre-historic people, really, because making some kind of architecture back then was like them making their own caves(shelter/home). Making their own caves also represented their ability to take control of nature to a certain extent.
The Neanderthal construction above is interesting for that reason; but also, the fact that they used pre-made elements from nature. They had not yet figured out how to shape, maybe even engineer the material itself(to be stronger, or more flexible and so on).
Note for the day, Gospel of Truth has been updated - see the "latest Gospel of Truth" below 1/21/16 post.