This ruined medieval castle sits high on a hill overlooking Sion, capital of the Swiss canton of the Valais. Originally built in the thirteenth century, it was finally abandoned in 1788 after a fire burned it down. The stones were used for surrounding buildings until the 19th century, when it was declared a historical monument. As far as I know the castle was never captured, which isn't surprising when you see the place: its hillsides are sheer.
The ruins are great fun to explore and one of the rewards for making the steep climb to the summit. Another is the chapel containing medieval area paintings. But maybe the best rewards are the spectacular views of the Valais, Sion, and the river Rhone.
Note the absence of railings in the last picture... You'd never see that in the US! I love living there but I think Europe in general has a much saner attitude to risk.