Diane's birthplace, the Chateau de Saint-Vallier, still overlooks the Rhone River as it passes through this small French town south of Lyon. Originally a monastery, it had been in Diane's family since 1270 when Aymar IV de Poitiers, Comte de Valentinois married Hippolyte de Bourgogne, Dame de Saint-Vallier. Here is a view of the chateau in the 18th century:
Diane inherited the chateau upon the death of her brother, Guillaume de Poitiers.
Directions to Saint-Vallier by car: From the north, A7, Chanas exit (#12); from the south, A7, exit Train l'Hermitage (#13). The chateau can be easily reached by Rue de Remparts, or, naturally, Rue Diane de Poitiers.
The chateau is easy to spot on Google Earth: