In recent months, ceremonies have been held to mark the centenary of major World War One battles at Verdun and the Somme in northern France. Hundreds of thousands of men were killed there as millions of artillery shells were fired by each side. Today, just below the surface of the battlefields, there are still countless munitions, as well as the remains of those soldiers whose bodies were never found. Our team met with bomb disposal experts and archaeologists. >> On France24.com: Our forefathers who fought at the Battle of the Somme