The Château de Landskron is situated in the southern part of Alsace, in the east of France, mere footsteps away from Switzerland, in the commune of Leymen. The village situated at the north of the ruin, Leymen, in the département of Haut-Rhin, lies in France while Flüh, at the south east foot of the ruin, is in Switzerland.
The castle was built before 1297. It had a very important strategic position in that it allowed the control of the Eastern Sundgau, the elbow of the Rhine and the city of Basel. Several disputes concerning the ownership have been reported. Like the Château de Ferrette and Château de Morimont, the Château de Landskron was owned by Habsburg for a time.
Wikipedia https://en.wikipedia.org/wiki/Château_de_Landskron
Address 68220, France
Coordinates 47°29'18.255" N 7°29'26.577" E