The Crawford's two-storey extension is almost complete. Designed by Dutch architect Erick van Egeraat, it is a soaring structure that slots into a difficult, wedge-shaped site, previously a courtyard, linking two wings of the existing building. From Academy Street it offers the striking prospect of a gravity-defying, billowing curtain of brick suspended over a glass wall. This pattern is echoed inside, as light filters softly through a roof shaped into a series of wave-like curves. In fact van Egeraat's inspiration was the sea, Crawford curator Peter Murray explains.

"It's akin to a series of waves, culminating in the breaking wave as we reach the street." The white plaster forms are also strongly suggestive of billowing sails. Appropriately enough, the shop opposite features an array of surfboards in its window.

It is a very bold design, creating a stepped, amphitheatre space on the upper level and a less dramatic but still spacious area below, interrupted by a set of rectangular columns, with oblong lights set into the ceiling. As an antidote to the curvilinear emphasis above, the downstairs is a tribute to the rationalist design principles of de Stijl. "We wanted a new building that would bring together the two parts of the old building without interfering with either," Murray notes, "and van Egeraat's design accomplishes that ingeniously in a variety of ways, while being uncompromisingly 21st century in spirit itself."

While the extension is spectacular, it is very much architect-led, and it will be interesting to see how it fares as an exhibition area. Currently, the official launch is set for June 20th, when Peter Mandelson is due to open 00 44, a major exhibition of work by Irish artists resident or previously resident in Britain. This show, curated by the Crawford in exile, so to speak, has already been seen in the US and at Belfast's Ormeau Baths Gallery. With its huge range of media, it should provide an effective road-test for the new, integrated Crawford.