Tourbillon Castle stands on the higher of Sion's two rocky hills, its ruined towers and walls open to the sky and to the wind that sweeps the valley. Built in the 13th century by the Bishop of Sion, it was burned down in 1788 and never rebuilt. The ruins are deliberately unrestored, which makes the site feel more immediate than many Swiss heritage attractions — there is nothing between you and the stonework but 700 years of weather.
The views from the top are exceptional: down into the floor of the Rhône valley, across to the Valère hill opposite, and up to the permanent snowfields of the Alps on both sides. The site is free to visit and the walk up from the old town takes about 30 minutes via a well-maintained path. Go in the afternoon when the light hits the valley from the west.
story: "The bishop who built Tourbillon in 1294 was one of the most powerful secular rulers in what is now Switzerland — the Prince-Bishops of Sion controlled the whole of Valais for centuries, their authority over the mountain passes giving them leverage over everything that moved between Italy and the north."