A work in progress: Museum of Fine Art, Boston

The newly opened Dh1.8bn renovation and expansion of the Museum of Fine Art, Boston, by the architects Foster + Partners has revitalised the institution by building on its strengths.

King Lear, which was in the MFA’s library, unknown to the public, until the new wing opened, was painted in London by the American Benjamin West in 1788.

The Boston Tea Party was a protest in 1773 in which colonists boarded a British ship and threw bales of tea overboard to protest against taxes. Events such as the Tea Party (revived in the recent electoral upsurge against President Barack Obama) showcase Boston as the crucible of the American Revolution.

Given the city's historical relationship with Britain, it may seem improbable that British architects - Foster + Partners, overseen by a British-born museum director, Malcolm Rogers - were put in charge of a $500 million (Dh1.8bn) expansion and renovation of the city's venerable Museum of Fine Arts's Art of the Americas wing.

But it is no more improbable than British architects building anywhere else today, said Norman Foster.

The approach, evidenced in the new wing, was to build on the MFA's strengths, Lord Foster said at the building's dedication in Boston on November 12. "We wanted to develop the strong personality of this museum, which is about the interaction of the buildings, which have been built up over time, and the incredible collections.

"We were making an architecture that serves the collections, and is flexible - a bold strategy with a light touch."

The MFA opened in 1876. Its last master plan dates from 1909, a century ago. Between that plan and the Foster + Partners design, the institution has grown in multiple accretions. Like at many American museums, these sharp-elbowed sections can create more chaos than harmony.

Yet the task for Foster + Partners in its master plan is preservation as well as expansion. While construction of the new wing was underway, conservators worked on the restoration of the exquisite Sargent Mural Rotunda, a circular gallery with extruding corridors decorated with classically themed murals and bas reliefs that the American painter John Singer Sargent created between 1917 and 1925. The gallery, rising into a dome 21 metres high, is one of America's greatest decorated interiors. Sargent (1856-1925), one of his generation's leading portraitists, considered the murals in the rotunda to be his most important work. The restored rotunda reopened a year ago.

Beyond the Sargent Rotunda, a minimalist visitor's centre opens into what's new from Foster + Partners, an enormous four-storey glass and steel cube. Beneath the ground level are temporary exhibition galleries where two Chinese exhibitions are now installed. To the east, a staircase leads to four levels of galleries for the MFA's Art of the Americas collection, one of its five curatorial departments. Beyond those galleries are glass-enclosed walkways that offer views towards downtown Boston, and toward the Fenway (or Fens), a park to the north.

Norman Foster calls the addition of a vast public space and new galleries "a crystal spine" that returns the museum to its original axis, simplifying what had been inscrutable labyrinthine circulation. Extending westward from Foster's glass and steel cube, the box-like volumes that hold the new galleries are sheathed in Deer Isle granite from Maine that sparkles in the sunlight.

The Foster atrium sits on land that had been an open-air courtyard. The space's glass walls are bordered on two sides by long narrow gardens. The lush planted areas are not mere landscaping, but necessary buffer corridors because of seismic instability - a surprise to many who never experienced earthquakes in Boston.

A newly installed Egyptian gallery is steps away on one side. European art is reached from the other side of the atrium.

Natural light fills the vast new cube. It also illuminates the walkways that surround the adjacent new galleries. "Although many of the galleries are by definition inward-looking spaces, we wanted to give the visitor the feeling that they had actually been in a building that had views, so we very deliberately devised these long colonnades on each of the floors looking out over the Fens," said the architect Spencer De Grey, who has worked with Norman Foster for 37 years. "You had a feeling of being in a transparent building, although your experience in the galleries was much more introverted."

Introversion, De Grey noted, was where the architects began: "This was a quite formidable building from the outside, which seemed fairly impenetrable, and when you got inside, it was very dense, and not at all generous."

Doors that once opened to the Fens on the north were closed for decades, after a man entered there, wrested a painting from the wall, and ran out the same doors. The doors reopened two years ago, as part of the new master plan's emphasis on access and openness. Security has improved inside and out, museum officials stress.

The completed wing reflects a collaboration of almost a decade between the MFA and Foster + Partners, who have renovated historic spaces in the Royal Academy in London, in the Reichstag in Berlin, and the Hearst office buildings in Manhattan.

"We never do the same thing twice," said Spencer de Grey. "The challenge of rejuvenating and refocusing historic buildings is something that we enjoy and that we get a great kick out of."

Boston's goal, Malcolm Rogers said, was to exploit that experience at Foster + Partners, but also to ensure that fresh ideas fuelled the new wing and the master plan.

"We didn't have a competition. We felt that if they could do models of what they wanted, it would fix their thinking too early," noted Rogers, 62, who has been director since 1994.

Inside the courtyard, the only work of art was Artificial Rock #85, a massive stone-like sculpture by the Chinese artist, Zhan Wang. The space is designed to be flexible, but seems more likely to accommodate events and eating than exhibitions. If the MFA needed something more urgently than light, it was a place for the museum's annual one million visitors to gather.

Inside the new American galleries, visitors are met by the informal 1770 portrait of Paul Revere, the American patriot who warned colonists of the approaching British troops, painted by the Boston artist John Singleton Copley (1738-1815). Revere, a silversmith by trade, posed with a silver teapot in his hand. In the room, silver objects by Revere are on display. Other Copley works are on view, including Watson and the Shark (1778), the dramatic scene of the young swimmer Brook Watson being rescued after a shark attacked him in Havana harbour. It should be noted that the film Jaws is set in Massachusetts.

Copley painted that monumental picture in London, and the artistic relationship with Britain runs throughout the new Boston galleries designed by the London architects.

King Lear, an equally dramatic scene from the Shakespeare play, was also painted in London by the American Benjamin West in 1788. The picture was in the museum's library, unknown to the public, until the new wing opened.

On the floor above is The Daughters of Edward Darley Boit, John Singer Sargent's American update of Las Meninas by Diego Velasquez. Across the gallery from that picture is the enormous Charles Stewart, Sixth Marquess of Londonderry,Carrying the Great Sword of State at the Coronation, which Sargent painted on commission in England in 1904. It was a 2003 acquisition from the corporate mogul Henry Kravis, explained Malcolm Rogers, who became a US citizen this year. Although Americans might tend to find the portrait pompous, the museum acquired the picture to cover the range of Sargent's career, he said. The MFA had owned some 500 Sargents, but lacked a full-length portrait of a man.

In an adjoining gallery, paintings covered every inch of the walls, salon-style, to reflect the practice of a century ago. "We know that visitors don't look at everything, anyway," said Rogers. "They go around like bees, stopping at one flower and not another."

The building's third-floor galleries encourage that kind of viewing, as they mix paintings, drawings, sculpture, furniture, costume and musical instruments. "The top floor of the wing is for 20th century American art, which has traditionally been a weakness for the museum, except in certain areas," Rogers admitted. There wasn't a painting to be seen by Fairfield Porter, the realist who achieved elegant harmonies of light and colour observed on the Maine Coast. Nor was there a work by the recently deceased Jack Levine, whose realism leaned toward the grotesque. A painting on view by Norman Rockwell, the New England artist par excellence for many, was on loan to the MFA from the Norman Rockwell Museum in western Massachusetts. The MFA doesn't own one - not yet at least, said Rogers.

"The galleries - and the wing - are a testament to our good intentions. It's not a statement of completion," Rogers said. "There are all sorts of areas where the galleries are going to need strengthening. So we hope that when people see what's been done, they'll say, 'We can help'."

Rogers stressed that donations of art were on the rise, which sets the MFA apart from most US museums these days. There will be more galleries to fill. The contemporary wing, a renovated addition originally built by IM Pei in 1984, is due to open in late 2011.

With the opening of the courtyard and the Art of the Americas galleries, more than half the work of the master plan is completed.

"The ultimate compliment somebody paid us was 'it feels natural, as if it's been like this forever'," Lord Foster said.