This year, the Metropolitan Museum of Art completed its latest great improvement: the restoration of its Fifth Avenue facade. The $12.2 million project has helped focus attention on the Met’s own building as one of the museum’s priceless artworks. It also represents the intersection of three trends in New York in recent years: museum renovations, building restorations, and nighttime illuminations of outstanding buildings.

As for the first, God bless the Met for not falling prey to the delusion that Renzo Piano can improve upon McKim, Mead & White – or Richard Morris Hunt. As for the second, God bless the Met for not treating its building as though it were some souvenir tchotchke suited as a backdrop for advertisements and laser light shows. Finally, go there at night for a genuine thrill. The exterior illumination is dramatic – calling to mind, though more beguiling than, the floodlighted Grand Central Terminal, the Met Life Tower, the former Tiffany building at 37th Street, and a few others. By day one wishes to enter the museum to see the wonders within. By night, there is a special feeling in contemplating the treasure house and only being able to wonder, dreamily, what its glorious halls must be like emptied of people and silent but for the padding feet of the night watchman.

Not the least of the facade’s present charms is its conspicuous absence of banners advertising the shows within. Hunt’s facade wasn’t designed with such large banners in mind, and they do damage to the architectural effect. I’m hoping the Met continues to feel they are not warranted.

The renovation of the facade, the first in the museum’s history, started with a rehabilitation and restoration of the roof. Then, to facilitate in the cleaning of the facade, workers removed the large banners that advertise the current shows. “When the renovation got underway, Philippe de Montebello noticed how much light came into the Great Hall,” a museum spokesman, Harold Holzer, said.

That observation led to the decision to reduce the size of the banners, so that they would no longer cover the windows and block the light. “In the ’70s, the Met was the first to put banners on the front. Maybe we’ll be trend setters again,” Mr. Holzer said.

Museum expansions and renovations take up a lot of space in the news. A couple of years ago, all of New York was talking about the Museum of Modern Art. This month, it’s the Pierpont Morgan Library. Both institutions willfully jettisoned their traditional identities so as to attract ever greater numbers of visitors and to appear to be au courant. In contrast to MoMA and the Morgan is the Frick Collection, which has yet to build a glass-walled modern addition. Indeed, in the late 1970s when the Frick felt it needed to expand, it did so with an addition, designed by the estimable John Barrington Bayley, that was perhaps the most consummately skillful piece of classical architecture erected in Manhattan in 30 or more years. The visitor is scarcely aware that it is not part of the original building – the sort of thing that horrifies some of today’s design intellectuals. Also to be noted is the Jewish Museum, which when it expanded in the 1980s verily replicated its existing building (the former mansion of Felix and Frieda Warburg).

In 2006, the antidote to the Morgan expansion is to be found at the Met, New York’s largest and greatest art museum. No, the Met has not expanded. It did a lot of that in the 1970s and 1980s.Those expansions, designed by Kevin Roche John Dinkeloo and Assocsiates, seemed kind of iffy when they were done, encroaching upon Central Park in what seemed somewhat insensitive ways. Yet by the standards of what has come since, those five lobes stuck on the rear of the Met – the Michael C. Rockefeller Wing, the Lehman Wing, the Lila Acheson Wallace Wing, the Sackler Wing, and the American Wing – seem remarkably understated and benign. They may have been modern, they may have usurped parkland, they might have been more sensitively adapted to the park – but they were not preening, show-offy additions, they were not, blessedly, “design statements.”

Those additions were conceived in the controversial directorship of Thomas Hoving, and completed under Philippe de Montebello. For me, the best of the additions completed under this vast program of expansion is the Petrie European Sculpture Court, which preserves the facade of a long-ago Met expansion by the architect Theodore Weston, while opening up the only properly framed view there is of the unconscionably misplaced and neglected Obelisk in Central Park, helping to provide something like a proper setting for what few people seem to realize is one of the handful of the most important objects in New York City.

But it is renovations of a lesser scale though greater loveliness that have been undertaken under the Montebello regime that have secured the Met’s standing as the great conservator of our cultural values. In particular I have in mind the thorough redesign of the European Paintings galleries completed in 1993. The Andre Meyer Galleries had only been opened in 1979 but were a disaster. Montebello and company had the great good sense to hire the brilliant Philadelphia architect Alvin Holm, a correct classicist, to design new galleries that are likely New York’s best conceived and executed galleries for the display of paintings since the Frick Collection opened in the 1930s. Just as good as, if not better than, those galleries are the Greek galleries that were dramatically redesigned in 1999. I remember the New York Times art critic Michael Kimmelman’s beautiful characterization of those galleries as “deeply, admirably unfashionable.”

The Met’s first building in Central Park opened in 1880. It was a Victorian Gothic affair concocted by Calvert Vaux and Jacob Wrey Mould and, unfortunately, perhaps the least felicitous of their contributions of structures to the park Vaux had laid out. Remarkably, one wall of the original museum can still be seen, within the Lehman Wing. After further additions, including the aforementioned one by Weston, which shifted the museum from Gothic to classical, the Met, just as it had begun to attain world-class significance, hired one of its own founding trustees, the incalculably important 19th-century architect Richard Morris Hunt, to design a new front for Fifth Avenue. Hunt’s design can be seen in the central section, with its stately but immensely welcoming colonnade. (Hunt also designed the majestic Great Hall within.) This was one of Hunt’s two great commissions just before he died, the other being the improbable mansion, “Biltmore,” of George Washington Vanderbilt, in North Carolina. It is also one of shockingly few Hunt buildings still standing in New York City. Alas, he died before it was completed, and his son, Richard Howland Hunt, completed it.

After J.P. Morgan became president of the trustees in 1904, the Met undertook to expand to north and south along Fifth Avenue. For these wings, the Met hired McKim, Mead & White, specifically Charles Follen McKim, who was also not coincidentally at work on Morgan’s private library on East 36th Street.

Today, the Met, illuminated, can be viewed as an object of great aesthetic significance in itself. No floodlight is trained directly upon the building. Rather, spotlights depend from among the rosettes of the soffits so as to cast white light vertically upon Hunt’s four leisurely paced pairs of Corinthian columns. In addition, the grand stairway is illuminated by lights placed on the undersides of the railings leading from the top of the stairs down to south, east, and north. The lighting also indirectly casts a glow upon the wonderful masks and other sculpture by Karl Bitter adorning the facade.

By day, amid the crowds on the sidewalks and stairs, a lot of the fine features of the facade don’t register. At night they awaken, just as the fewest people are around to see them. Imagine – a museum doing something not meant to attract crowds. What’s more, the simplicity of the scheme will appear modern and dazzling long after the front of the Brooklyn Museum comes to appear a shopworn, dusty vitrine.