The earliest mention of the castle can be found in the deed of the Count Rudolf von Werdenberg-Sargans for a sale to Ulrich von Matsch. The then owners - presumably also the builders - were the Counts of Werdenberg-Sargans. The Bergfried (12th century) and parts of the east-side are the oldest. The tower stands upon a piece of ground of about 12 x 13 m and has a wall density on the ground floor of up to 4 metres. The original entrance lay at the Hofzijde at an 11 metre height. The chapel St. Anna was presumably built in the Middle Ages as well. The main altar is late-gothic. In the Schwaben War of 1499, the castle was burned by the honorbound of Switzerland. The west-side was expanded on by Count Kaspar van Hohenems (1613-1640).
The Liechtenstein family acquired Vaduz Castle in 1712 when it purchased the countship of Vaduz. At this time, Charles VI, Holy Roman Emperor, combined the countship with the Lordship of Schellenberg, purchased by the Liechtensteins in 1699, to form the Principality of Liechtenstein.
The castle underwent a major restoration between 1905 and 1920 during the reign of Prince Johann II, and was expanded during the early 1930's by Prince Franz Joseph II. Since 1938, the castle has been the primary residence of Liechtenstein's Royal Family. It is not open to tourists." - in: wikipedia