He Knocked Down a Wall and Found a City. It Wasn't Empty.

In 1963, in the town of Derinkuyu in central Turkey, a man was renovating his house. He knocked down a wall.¹

Behind it was a passage. The passage led down. And down. And down.

It led into a city.

Derinkuyu is carved entirely out of soft volcanic rock. It goes more than eighty meters into the earth, through at least eight levels.² It has stables for animals. Kitchens with blackened ceilings. Wine and oil presses. Wells. Chapels. Schools. More than fifty ventilation shafts keep the air moving, so fresh that a candle still burns at the bottom.²

Historians estimate it could shelter around twenty thousand people, along with their livestock and food.²

Nobody knows exactly when it was first dug. Parts may be nearly three thousand years old. It was expanded over centuries and used as a refuge by Christians during the Byzantine era, when raiders swept across the region.³ Tunnels connect it to other underground cities nearby. There are more than two hundred in the region.³

And every level can be sealed.

At the entrances between floors stand huge round stone doors, like millstones, up to a meter across and weighing as much as five hundred kilograms.² They roll across the passage in a groove. They can only be moved from one side.

The inside.

Defne Arslan surveyed buildings for a living, and in Cappadocia that meant caves. Half the hotels in the region were carved into rock. Tourists paid extra to sleep in them. Engineers like Defne made sure the rock would not come down on their heads.

A cave hotel in Nevşehir Province was expanding. The owner wanted to break through a back wall in Room 9 to make a suite. Defne was there to check the rock first.

She tapped the plaster with a hammer and heard the hollow sound immediately.

She did what the man in 1963 had done. She made a small hole. She shone a light through.

A passage. Sloping down. Old. The walls were covered in the marks of hand tools, thousands of tiny curved scars where someone had chipped the stone away, one stroke at a time.

At the end of the passage, maybe twenty meters in, was a round stone door.

It was closed.

The hotel owner wanted to call the tourism ministry. A new underground city would be worth more than every suite in the province.

Defne went in first, alone, to make sure it was safe. That was her job.

The passage was tight. She went bent over, then on her knees. The air was cool and dry and smelled of dust, and it moved. Fresh air was coming from somewhere below.

The stone door was a perfect circle, taller than her, sitting in its groove. She put her hands on it and pushed. It did not move. Of course it didn't. It was built to be moved from the other side.

Beside the door, in a small niche, someone had left a clay oil lamp and a sheet of paper, folded and weighed down with a stone.

The paper was not old. It was a page from a field notebook, the kind surveyors use, written in pencil. Half in Turkish. Half in English.

It was dated 1963.