Where: Hohenschwangau, Germany
Most important renovation: 21st Century
Accessible: yes, interior with guide
Arguably, the most famous castle in the world.
This historicism castle was built by order of King Ludwig II of Bayern. He thus brought the state of Bavaria to the brink of financial collapse.
Due to the mysterious death of the king, the castle was never completed. It was opened to the public only six weeks later, in order to recoup the costs. It has since attracted millions of visitors every year.