This is Qasr al Ferid, or ‘lonely castle,’ the largest of some 100 tombs here in the ancient Nabatean city of Hegra, now known as Mada’in Saleh. This site in Saudi Arabia is considered an archeological treasure for its well-preserved remains dating back nearly 2,000 years, when the Nabatean Kingdom flourished by trading incense, myrrh, and spices. While this particular tomb was never completed, its four-story size indicates it was intended for someone wealthy and powerful.