Najaf is considered the third most holy city in the world. (Saudi Arabia’s Mecca and Medina rank as the top two.) Meaning “a high land” in Arabic, Najaf is located 110 miles south of Baghdad and holds within it 600,000 residents and the revered Imam Ali bin Abi Talib mosque.

Named for the murdered cousin and son-in-law of Islam’s prophet Muhammad, the mosque has been a place of pilgrimage for Shiite Muslims for centuries. Built in the year 977, it sits atop both the bodies of Ali, for which it is named, and Adam, the biblical first man. Sprawling from the outskirts of the mosque is the world’s largest cemetery, the Wadi Al Salam or Valley of Peace.

The cemetery, which dates back to the 7th Century, holds some 5 million dead Muslims. It spans nearly five square miles, yet the area is so congested with tombs that the bodies lay only inches apart, and the grave markers lean together. Dirt paths crisscross the cemetery’s concrete and brick tombs. Some have Arabic inscriptions while others are marked by locked doors or stairs that lead to underground rooms. There are caged, turquoise crypts with framed black and white photographs of the dead hanging inside.

The Wadi Al Salam cemetery is a coveted burial ground for Muslims. About a dozen new burials take place on the site per day, and some of the most recent ceremonies were for victims of Saddam Hussein’s secret executions, recovered from mass graves and moved into the cemetery.