years later, they opened Galerie Ileana Sonnabend on in Paris, where she introduced art by Andy Warhol, Roy Lichtenstein and others, and helped establish a European market for their work. In 1965, they acquired an additional apartment on Ca' del Dose in Venice. In 1968, the couple closed the Paris showroom and moved back to New York. At one time, the couple thought that Michael Sonnabend would run the New York gallery while Ileana oversaw their Paris establishment, but he soon found that the art business did not suit him. In 1971, she opened the Sonnabend Gallery, in a building at 420 West Broadway in Soho. The industrial chic restoration instantly became the center of the emerging SoHo art scene. She inaugurated her gallery with a performance by Gilbert & George. She exhibited American artists like Jeff Koons and Vito Acconci, and introduced European artists like Christo, Georg Baselitz, and Jannis Kounellis to U.S. audiences. When the performance artist Vito Acconci announced that his performance piece Seedbed called for him to masturbate in her gallery for two weeks in 1972, Sonnabend simply replied, "You do what you have to do." In 2000, after she had closed her other galleries, Sonnabend and her adopted son Antonio Homem moved the SoHo gallery to West 22nd Street in Chelsea. Collection After Sonnabend died in her Manhattan home in October 2007 at the age of 92, the estate tax return pegged her total worth at $876 million, triggering a $471m tax bill. Her heirs subsequently sold a portion of her postwar-art collection for $600 million—reportedly the largest private sale in history. Although the family had been in talks with the auction houses, they chose to sell parts of the collection privately because of the uncertainties surrounding the financial markets during the 2008 crisis. Backed by members of the Al Thani family, the art-dealers collective GPS Partners purchased $400m of paintings and sculptures dating mainly from the 1960s on behalf of private clients. This first cache is said to have included Jeff Koons's 1986 sculpture Rabbit, which has been valued in excess of $80 million, as well as Roy Lichtenstein's cartoon painting Eddie Diptych (1962), Cy Twombly's abstract Blue Room (1957) and Andy Warhol's Silver Disaster (1963), one of the artist's paintings of an electric chair. The second transaction, a selection of paintings by Warhol, was sold to Gagosian Gallery for a reported $200m. Among