Once upon a time ...
Original image with thanks to Shadowgate
I used 'outlines' and 'shadows' to get the effect of a drawn tower. If you want some more information about how I made the tower look 'illustrated', you can find it here.
Textures & background thanks to
The painting & the story of Diane de Poitiers can be found on Wikipedia. Diane was the mistress of a French king, Henri II. He was married to Catherine de Medici. During his life he gave Chenonceau (amongst lots of other gifts) to Diane. When the king died in a bloody game Diane was immediately banished by Catherine from the castle.