What sort of background information does Langdon give on Da Vinci in this section of the book?

In this section of the book, Langdon educates the reader that Leonardo Da Vinci knew of the location of the Holy Grail and that there has been much conjecture among art historians about whether he hid clues to the Grail's whereabouts in his paintings. For example, the landscape in the Madonna of the Rocks has been said to look like Scotland or that the order of the disciples at the Last Supper represented a clue.