A Thousand Skulls As A War Relic

Does anyone have any idea of the name and location of this ossuary? It looks like some kind of World War One monument. The photo is part of the cd inlay for Sunn 0))) magnificent "Black One" album, and bears the legend "A Thousand Skulls As A War Relic". The flag in the picture might have provided a clue, if it were possible to determine the nationality - but alas, it is not.

Here is a link to an article on the use of human bones by a Belgian Surrealist as an intervention against the political cult of the dead.