ZURICH (REUTERS).- Over the past half-century the Nahmad family's primary relationship with art was how much money they could make by dealing in the works of Picasso, Monet and Dali.

Now a new exhibition, "Miro, Monet, Matisse - The Nahmad Collection" reveals for the first time the world-class works they stashed away, almost forgotten in a warehouse.

Their story began in the early 1960s, when brothers Ezra and David began buying art in Paris and transporting it back to Milan to sell.

On one occasion they drove through the night with a Picasso strapped to the roof of their Morris Minor car, because it wouldn't fit in the trunk, Ezra's son Helly said in an interview for the exhibition's catalog.

"When they arrived in Milan, they discovered to their shock that the painting was no longer there -- it had blown off on the motorway. They drove straight back and luckily found the picture -- lying damaged in grass on the roadside," Helly said.

For the older generation of the Nahmad family this autumn's exhibition is the first chance to show their children what they've achieved, the show's curator Christoph Becker told a media briefing.

Since most of their purchases head straight from the auction house to the depot, the family members have never seen some of the paintings and only have a piecemeal overview of what they owned, he said.

Concentrating on the period from 1870 to 1970, the exhibition spans impressionist watercolors by Monet through to 14 brightly colored psychedelic canvases by Spanish artist Joan Miro, including many rarely seen works.

Among the highlights is Pablo Picasso's painting of his son in a harlequin costume: "Le Petit Pierrot aux fleurs" (1923/1924). The soft, pastel colors contrast with the abstract, bulbous figures of his later work, also on display.

Elsewhere, Amedeo Modigliani's elongated figures rub shoulders with explosions of colors and shapes in Wassily Kandinsky's abstract works.

Some artists are equally notable for their absence, Becker said. Although the family made a lot of money dealing paintings by Salvador Dali, none of his oeuvre is included in the exhibition.

Becker declined to speculate on whether the Nahmads will make the collection accessible to the public on a more permanent basis, but added that the exhibition had kindled an awareness of how significant the works are as an entity.

"Miro, Monet, Matisse - The Nahmad Collection" runs at the Kunsthaus Zurich until January 15.

(Reporting by Caroline Copley, editing by Paul Casciato)