The de Baysers are third-generation experts in authenticating and valuing fine artworks. In 2016, Patrick de Bayser played a key role in the discovery and authentication of an original drawing of Saint Sebastian by Leonardo da Vinci, now valued at more than $15 million. Get a chance to see art history in the making with exclusive access to the de Bayser gallery, library, and offices all housed within the 17th century mansion that once housed the children of the notorious marquis de Louvois.