There are existence of such architectural masterpieces that hints at how modern our ancestors were.  There are architectural masterpieces that makes us question is our modern technology actually modern.

1. Stonehenge:  It is a prehistoric architectural marvel, made at such a time when there were no written history records. This structure is present in Wiltshire, in England's Salisbury plain and is considered as the most awe inspiring engineering marvel in the world. This structure took 1500 years and three phases to get completed . There are two small holes in the circumference of two circular pits which are called as aurbey hole. In these one metre deep holes many human bones were found. Not much has been discovered about the first and second phase of it's construction. In third phase the real form of this structure unfolded.In the third phase of it's construction 150 km away from preseli hills, wales some bluestone were brought whose weight was four tonnes and then they were arranged in concentric circles. But here something to wonder about is that how were such big stones brought from so far away?? This still remains a mystery. Some theories also claim that a magician named Merlin from the Arthurian made Stonehenge from his magic. And others are of the belief that the thirty feet tall structure of Stonehenge were assembled by giants. Some scientists are of the opinion that it was built around 11,000 to 12,000  years ago by some hunters and gatherers in order to spend time.
2. Gobekli: Turkey's gobekli tepe is known as the world's oldest temple. Many things about this structure made around 9000-8000 BCE are still undiscovered. We just know that this was made way before agriculture and animal domestication. German scientist Klaus Schmidt had discovered this structure in 1994 and it's discovery hinted at it's religious significance. This shocked archaeologists because it hinted at the fact that humans started practicing religion long after taking up agricultural practices. This sight roughly looks like a circular arrangements and it is believed that many such enclosure have been buried under the ground. By using computer algorithm a group of scientists digitally analysed this structure. Their conclusions turned out to be very shocking and revolutionary. In the exact centre of every circular wall there were pillars and the three structures that they had discovered when joined by their midpoint formed a perfect equilateral triangle. This hints at the fact that geometry existed even 11,000 years ago.