I´ve seen this location around social media since a couple of years and wanted to visit it so bad. Is called Castillo de Zafra, a 12th-century castle located in the municipality of Campillo de Dueñas, in Guadalajara, Spain.
It is said that its sky is one of the best and most dark with no light pollution one in Spain, and yes, I can assure it. I was in awe both contemplating the haunting shape of the castle and the amazing and clean milky way behind it.
This location was also used in Game of Thrones as the "Castle of Joy", where Jon Snow was born.