On September 17, 1961, Dag Hammarskjöld, the Secretary-General of the United Nations, was traveling on a mission to help broker a peace deal for the civil unrest raging in the Democratic Republic fo the Congo. He was flying, along with 18 other members of the UN staff and other international officials, to Ndola to meet with the prime minister of Katanga Province.

As the plane was preparing to land in Ndola, it crashed, skimming the tops of the trees and finally hitting down near an anthill. A fireball was seen from Ndola, but rescue personnel were unable to reach the site until daybreak. Dag Hammarskjöld’s body was found in a seated position at the foot of the anthill, and the other passengers were people found closer to the wreckage.

In the years since, there have been several investigations into the crash trying to determine whether the plane was sabotaged or shot down, but no conclusive evidence has ever been found.

Today, an expansive memorial stands at the crash site. A plaque marks the exact spot at the foot of the anthill where the Secretary-General’s body was found, and a monument surrounded by quotes from Dag Hammarskjöld commemorates the mission of the plane’s passengers. A small museum at the site explains the circumstances of the peace mission and the crash, and the work of the United Nations.