At the heart of the Château de Chambord lies a double helix staircase designed by Leonardo da Vinci. It is, in fact, two staircases that begin opposite one another, neither visible from the other. From the ground floor of the massive chateau, these two staircases wind around a central illuminated well, visible to each other only in glimpses through small opposing windows. They twist up to the top of the chateau where they meet in the roof. Legend suggests that this configuration was designed so that Louis XIV, the Sun King, could arrange clandestine meetings with his mistresses at the top. The steps are supposed to be sufficiently shallow that a lady will not tire in ascending them.
One woman I travelled with found the staircase so strikingly symbolic of the marital disharmony and disconnect that resulted in her divorce that she declared the beautiful architectural feature the ugliest place in the Loire. If you visit, have someone you know take the other staircase. The effect of looking over and glimpsing someone on the same plane, going in the opposite direction, and then seeing them disappear, only to reappear in the window another floor up, and finally to suddenly encounter one another, face-to-face, at the top, is uncanny. It feels as though you’ve just taken part in an optical illusion. Even when you understand how the staircase works, you are left with an impression that some sort of magic or trick has taken place.
(Palladio’s illustration of the staircase)