Where: Vianden, Luxemburg

Start of construction: 11th Century

End of construction: 17h Century

Most important renovation: 20th Century

Accessible: yes

Important fact:

built on the foundations of a Roman 'castellum' and a Carolingian refuge from the 8th Century.

Re-built between 1977 and 1990.

http://www.castle-vianden.lu/english/