1. castle
Castle on the Zollerberg in Germany. Home castle of the Hohenzollern. Build in the 11. century, it was destroyed 1423. After being build up again it was abandoned in the 18. century. Rebuild in the 19. century.
Now it is the Hohenzollern-Museum.
2. dynasty
First mentioned in 1061 the dynasty has been divided serveral times. The two main lines are the Frankish and the Swabian. Some of the Frankish later became kings (ex.: Friedrich II.) or emperors (ex.: Wilhelm II, whose sister married Konstantin I., king of Greece).
Some of the Swabians later became kings in Romania. In 1870 Spain offered Leopold I. (a Swabian), the crown, which he firstly accepted, but later gave back (without being crowned) because of differnces with France, which led to the war between Germany and France in 1870/71.
A closer look at the family register would show a big network in Europe. Most royal families are somehow related to the Hohenzollern.