Previously unknown paintings by Henri Matisse, Marc Chagall and Otto Dix are among a treasure trove of art -- much of it believed to have been looted by the Nazis -- found hidden in a Munich apartment.

The vast collection, which experts say has "a value so high it cannot be estimated," was recovered in a raid by German tax authorities, in connection with an investigation into tax evasion, in February and March 2012.

At a press conference in Germany on Tuesday, experts revealed that more than 1,300 artworks -- many long feared lost or destroyed, and some which had never been recorded -- had been discovered. Among the haul were paintings by Pablo Picasso, Henri de Toulouse-Lautrec, Oskar Kokoschka, Canaletto, Pierre-August Renoir, Franz Marc and Gustav Courbet.

Read more on CNN