I wouldn't consider myself enough of an expert on the topic to make an estimate of my own but I would not be surprised at all if u/RobFromTechServices isn't far off with his guess of 10,500 BC.

The somewhat recently discovered Gobleki Tepe in Turkey completely blew the lid off the mainstream narrative that civilization and megalitihic stonework only goes back about 6000 years. The site is about 50 times larger than Stonehenge and is carbon dated to be 6000 years older than any previously acknowledged manmade stone megaliths.

The Sphinx is also almost certainly thousands of years older than mainstream archaeologists and Egyptologists will admit based on the immense water erosion in the Sphinx quarry. The last time water would have flowed in sufficient quantities to cause that type of erosion in that location would have been around end of the last ice age, ~11,600 years ago. This was around the same time Gobleki Tepe was founded, and possibly Stonehenge as well.

To anyone who is not familiar with Graham Hancock and/or Randall Carlson, I would suggest checking out their appearances on Joe Rogan. Some of the most fascinating talks I've ever heard/seen..

Archaeology and geology will be a part of The Great Awakening as the lies we've been fed for generations are gradually dismantled and proven false.

I would bet about 10,500 BC.....