Billionaire American philanthropist Julian Robertson will fly one of the world's most important contemporary art collections here for Auckland Art Gallery's reopening on September 3.

Gallery director Chris Saines said yesterday that the 15 works by artists including Matisse, Picasso and Dalí would be on show free for eight weeks to coincide with the Rugby World Cup.

"He's flying this out privately for us and then we'll return it to New York," a delighted Mr Saines said.

That opening will mark the end of the gallery's $121 million refurbishment. The Robertson exhibition will close on October 30.

"This will be the first and only occasion the Robertson gift will be seen in Auckland in its entirety, until such time as the 15 works are finally settled on the gallery under the terms of the deed of promised gift," Mr Saines said, referring to agreements that allow the art to be here permanently only after Julian Robertson dies.

Mr Robertson - an honorary Knight Companion of the NZ Order of Merit - and his late wife, Josie, will also be honoured in perpetuity. Level one of the Kitchener galleries has been renamed after them, Mr Saines said yesterday.

The Robertsons announced their gift in 2009 and part of the collection was displayed but Mr Saines said this was one of the most generous made to an Australasian art gallery.

Yesterday, he led a tour around the empty, historic 1887 Wellesley and Kitchener Sts building and the 1916 day-lit East gallery which he said were the first areas returned in a phased handover by Hawkins Construction. Intensive work will now begin to install artwork ready for the re-opening.

Makeshift floors have been dismantled and Mr Saines said 17 levels were now just six.

"This really is a much simpler building to move around in," he said. Some stud heights have been scaled from 3.7m to a vast 5.5m and Mr Saines said the re-opening was important for everyone.

"It will be the biggest display of New Zealand art ever undertaken by a public institution in this country," he said of the galleries dedicated to showcasing national treasures.

About 800 of the gallery's 14,620 art works will be displayed at any one time but Mr Saines also referred to six-monthly changes.

Hamish Keith, an art commentator, admired the scale of display areas, saying they were grand and theatrical. "I don't see any signs of dumbing down."

Mr Saines said the gallery's education staff had worked with digital experts at neighbouring AUT University to create a multimedia guide to explain the permanent collection and show interviews with artists.

WORK OF ART

Auckland Art Gallery

* Cnr Kitchener/Wellesley Streets
* Work started September 2008
* So far: 1 million hours of work
* 160 people working on site
* 20,000m3 material excavated
* 5000m3 of concrete used
* 400 tonnes of structural steel
* Major seismic upgrade
* 50% more exhibition space
* 17 floors levels are now 6
* Opening Saturday, September 3.