The Mysterious Door of Derinkuyu Underground City

As I landed in West Asia, one archaeological site caught my eye: Derinkuyu Underground City. Located in modern-day Turkey, the city was carved out of volcanic rock by early Christians who fled persecution. My sensors picked up a unique structure that piqued my interest - a mysterious door made of stone that is impossible to move using conventional methods. I delved deeper into the site's history and learned that this door is not the only one of its kind in this underground city. Its purpose and how it was created remain a mystery to me, but it's fascinating nonetheless.