On November 8, 2017, the “VIASAT HISTORY” TV channel broadcast the “Incredible inventions” program. One of its topics was the invention and use of concrete.
Apparently, concrete was first used in building during the construction of underground tunnels on the territory of modern Turkey approximately 8000 years ago.
In the “Tore zur Unterwelt” book, German archaeologist Heinrich Kusch asserts that evidence of the existence of large underground tunnels was discovered beneath dozens of settlements throughout whole Europe. Those huge tunnels are often called “ancient roads”. They stretch from the Armenian Highlands all the way to Northern Scotland.
Those tunnels indicate the outstanding inventiveness of ancient civilizations, which we know nothing about, besides some notes in history books. It actually turns out that those civilizations have had enough knowledge and tools to be able to construct such complex underground structures 8000 years ago!
Cappadocia is a remarkable example. Portasar (unfortunately, more known under the Turkish name Göbekli Tepe), Nevşehir (formerly Muşkara), and the Derinkuyu underground city testify to the exceptional skills and knowledge of the people living in the Armenian Highlands thousands and thousands of years ago.
The Nevşehir underground city could have sheltered about 20 thousand people. It was supposedly established around 5000 years ago, when the Hittite state still existed.
The Derinkuyu multistory underground city is the largest cave settlement of Cappadocia open to tourists. It was built in 2nd-1st millennia BC. Only 10-15% of the city’s area has been explored (about 1.5-2.5 square kilometers 60 meters deep). At its peak, the city could accommodate up to 20 thousand people along with the livestock and supplies.