Written by Judith Vonberg, CNN Contributors Bryony Jones, CNN

The vast collection was uncovered in the home of Cornelius Gurlitt, the son of Hildebrand Gurlitt, an art collector who dealt in works for the Nazis. Experts believe many of the discovered paintings, drawings and sculptures -- including works by Claude Monet, Pablo Picasso and August Rodin -- were looted by the Nazis from Jewish collectors or dealers.

This week, more than 400 of these artworks will go on public display for the first time at exhibitions at the Bundeskunsthalle in Bonn , Germany and the Kunstmuseum Bern in Switzerland. Showcased alongside historical images and archive material, they shed new light on a dark period in Germany's history.

"We have a historical approach and an art historical approach, and also a moral approach," Rein Wolfs, co-curator of the Bonn exhibition, told CNN.

"The Nazi system of looting art played a very important role ... for Hitler, art had the charisma of being eternal and not disappearing. Whatever happens in history, art would remain."

A time of deception

During the 1930s and 1940s, thousands of works were stolen from Jewish families by the Nazi regime, or sold for a fraction of their true value as the owners tried to flee the country.

Researchers funded by the German government have been working for several years to trace the provenance of hundreds of the artworks in Gurlitt's hoard. But because many works were sold without any documentation, taxes or export licenses, their origins are difficult to trace.

"It was a time of deception," said Andrea Baresel-Brand, who has led the Gurlitt provenance project since January 2016. "Dealers such as Gurlitt disguised the path taken by these artworks."

She and her team are engaged in research on 735 of the pieces discovered in Gurlitt's apartment, with hundreds more still to be addressed. Wolfs hopes that the exhibitions will lead to a flurry of new claims from people who recognize the works as stolen.

An 'eerie feeling of happiness'

In 2013, CNN spoke to Cornelius Gurlitt's cousin Ekkehart , who described Cornelius as a "lonesome cowboy." He insisted the family had no idea about the treasure trove of paintings Gurlitt was hiding in his apartment.

German authorities were oblivious too -- until they raided Gurlitt's home during a tax evasion investigation in early 2012.

Before the discovery, many of the works were feared lost or destroyed, while others were entirely unknown to the art world. Experts at the time said the haul had "a value so high it cannot be estimated."

The collection was seized, but the works that weren't suspected of being stolen were later returned to Gurlitt. Just one month later, he died, leaving the masterpieces to Kunstmuseum Bern.

"To stand in front of these works, which have for a long time been thought missing, lost or destroyed and to see them in a relatively good condition -- in part a little dirty, but not damaged -- gives one a somewhat eerie feeling of happiness," art historian Meike Hoffmann told CNN soon after the discovery first became public.

Now it's not just historians who can experience that feeling.