According to Wikipedia: "The Liechtenstein Museum is in Vienna, Austria contains the art collections of its owners, the Princely Family of Liechtenstein, rulers of the principality of Liechtenstein. They include important European works of art, forming one of the world's leading private art collections. Its highlight used to be Leonardo's portrait of Ginevra de' Benci. A catalogue of the artists (with short biographies) featured in the Gallery at the time of Prince Joseph Wenzel was compiled by Vicenzo Fanti in 1767.
"The museum, which was open to the public until the Anschluss of 1938, had various locations, including the Liechtenstein Garden Palace in the IX District Alsergrund, Vienna, and the Liechtenstein City Palace in Bankgasse, Vienna. It was reopened on 29 March 2004 and, after battling with lack of tourist interest, was shut down in November 2011.
According to the official website, "the highlights of the princely collections can be viewed exclusively as part of an event package or a pre-booked guided tour"."