The double-helix staircase and the rooftop terraces

At the centre of the keep, the double-helix staircase runs up through all the floors as two separate spirals wound around a hollow core: two people can climb it at the same time, see each other through the openings, and never meet. It is attributed to Leonardo da Vinci, and it is the single most photographed interior in the Loire.

It is also a hard frame, which is why it rewards a plan. The stone is pale, the light comes from above through the lantern, and the geometry only reads if you shoot straight up the well or straight down it. A person on the opposite spiral, glimpsed through an opening, is the picture that explains the staircase; everything else is just a nice curve.

The stairs deliver you onto the rooftop terraces, and that is the second half of the location. Up there you are among the lantern turrets, dormers and carved chimneys — a small stone town at roof level, with the domaine's forest running to the horizon in every direction. Late afternoon light between the chimneys is the best of the day; the terraces are also the coolest place in the building in summer.

Practical: this is inside the château, so it is ticketed with fixed hours — check them, and check the current rules on tripods and on anything beyond a normal visit, which usually needs clearance. Interiors are busiest between eleven and three; the first and last hour of opening are much quieter. The staircase is a genuine climb, the terraces are exposed and windy, and the stone underfoot is slippery when wet.