The castle of Blancheforts sits atop a white rock in the south of France.

The donjon of this castle together with the church of Peyrolles
and the donjon of the castle of Arques form a perfect triangle of 30, 60 and 90 degrees.
Have these buildings been built in this pattern intentionally ?
If so, by whom were they built and what was (or is) the meaning of this triangle ?

You will find the answer in
"The Secret of Blanchefort"