If the 0 Meridien has to be marked by a tomb and not any tomb, then that tomb could have been in the Pyrenees.

^{Above - picture from (Google Earth) with thanks to Rennes‑le‑Chateau‑archive.com}

It seems the conflict between geographers had something to do with the Pyrenees. As Louis's the XIVth had decreed that the "The Pyrenees no longer exist!". 

Officially said in context of;

War of the Spanish Succession (1701-1714)

- Charles II of Spain (Spanish Habsburg) died without an heir
- before Charles' death, France and Austria signed a treaty to equally divide Spain
- Charles II named Philip of Anjou, grandson of Louis XIV, heir in his will
- Louis then ignored the treaty in favor of his grandson
- "The Pyrenees no longer exist"
- England Holland, Prussia, and Austria allied against France, Spain, and Bavaria
- Battle of Gibraltar
- Battle of Blenheim
- Treaty of Utrecht ends the war

If the 0 Meridien has to be marked by a tomb and not any tomb, then that tomb could have been in the Pyrenees.

? Related to the famous tomb of Rennes-les-Bains