A man tore down his basement wall and discovered an ancient underground city home to 20,000 people.
A guy from the Turkish region of Nevşehir decided to break down a wall in his basement one day in 1963 and ended up uncovering a massive underground metropolis.
The gentleman (not mentioned in the reports of the time) knocking down the wall with a sledgehammer found a tunnel, and beyond it, more tunnels. Further investigation revealed it to be an 18-story-deep underground city equipped with chapels, schools, and stables.

The city, also known as Derinkuyu, had been abandoned for generations. probably to the relief of the man who had just entered. Archaeologists from the Turkish Department of Culture estimate that the city, which housed up to 20,000 people, may have begun in the 8th and 7th centuries BC. c.
The rock, made up of volcanic ash deposits, was soft, a manuscript from around 370 B.C. C. that possibly describes Derinkuyu mentions that the underground dwellings were large enough for a family, domestic animals, and food.
The city reached its apogee in the Byzantine period (about 395 CE to 1453 CE), when it became a maze of tunnels, chambers and rooms, covering 445 km². The network of tunnels and passageways contained hidden entrances, ventilation shafts, wells, and water channels.
Round rolling stone doors might be used to shut the tunnels from the inside, and the corridors themselves were narrow to force invaders to line up one by one.