Considering the Le Manoir Saint Thomas in Amboise?
A VT member wrote the following comment about visiting Amboise:
Final Resting Place of Leonardo da Vinci by wanderlust23
"In this place lies the remains of Leonardo DaVinci."
Da Vinci's final resting place is said to be in the small chapel on the castle grounds at Chateau d'Amboise. He was a good friend to King Francois I and helped design parts of his castles/palaces.