Talk about a Grand Design!

In 1963, a Turkish man was renovating his home when he noticed his chickens were disappearing. To his amazement, he discovered that on the other side of his basement wall was a secret room he huned right out of the bedrock. As the man began to explore, he quickly uncovered a narrow passageway leading right down into the earth. It turned out he hadn't just found a secret room, he'd uncovered the entrance to an entire city, an entire underground city. Daren Kuyu constructed around 3,000 years ago. It is the biggest underground city on Earth. And it's thought to have once housed as many as 20,000 people, borrowing 85 m underground. Its labyrinth corridors sprawl across eight distinct levels with more than 50 ventilation shafts supplying fresh air and a central well offering a constant supply of clean water. The city contained hundreds of homes, a school, various meeting spaces, a church, dedicated rooms for livestock, and full-on wine and olive oil production facilities. There was even a dungeon. Some historians believe the first caves were dug by the Hittites, whose empire encompassed most of Turkey during the Bronze Age. Even more incredibly, it was in use for almost all of its 3,000year history, including as recently as 1909. Denuyu can be found in what is known today as the Capidoshia region of Turkey. You may already know that Capidoshia is famous for absolutely insane rock formations. It's those crazy rock formations known to geologists as hoodos that provide a clue as to how Daringuyu was built. Hudos only form under very specific conditions, namely when erosion gets to work on a thick layer of soft rock covered by a thin layer of harder rock. In the Capidoshia region, the soft rock is called tough. Capidosian tough is so soft it can be worked even with simple hand tools. And that's exactly how Darenuyu was built with basic tools, a bit of elbow grease, and an awful lot of time. Historians are largely in agreement that the residents of Darenu didn't live in the city permanently. But whenever a marauding band of angry types with big swords showed up, the locals would simply slip underground and out of sight. They had the facilities to stay down there for months on end. Evidence for this defensive use case is clear to see in the unique design of the city. The unique structure of the city made it practically impervious to attack. And since its inhabitants could stay underground for months on end without resurfacing. By the early 20th century, the locals were Capidosian Greeks. It was they who last used Aruyu as a refuge in 1909 after the Ottomans massacred tens of thousands of Armenians in the city of Adana. Fearing they might be next, the Capidoshian Greeks disappeared beneath the ground. During Kuyu isn't the only underground city in the Capidoshia region. It's one of more than 200. And some of these subterranean settlements are actually connected to one another. There are almost certainly more of them out