During the 300 days of the Battle of Verdun (21 February 1916 – 19 December 1916) approximately 300,000 men died out of a total of 700,000 casualties (dead, wounded and missing).

Through small outside windows, the skeletal remains of at least 130,000 unidentified combatants of both nations can be seen filling up alcoves at the lower edge of the building.

On the inside of the ossuary building, the ceiling and walls are partly covered by plaques bearing names of French soldiers who died during the Battle of Verdun.

In front of the monument, and sloping downhill, lies the largest single French military cemetery of the First World War with 16,142 graves.

At the top of the tower is a rotating red and white "lantern of the dead", which shines on the battlefields at night.