This column is best read as an open letter to the Metropolitan Museum of Art, calling upon that august institution to drop everything and stop what it is doing. Anyone who has visited the museum in the past few weeks will have noticed that most of the steps leading up to the main entrance on Fifth Avenue have been cordoned off with white linen fencing. According to the press department, this is in preparation for cleaning, restoring, and “rethermalizing” the steps.

There is nothing wrong with any of that, except that, when the work is complete, the steps will look exactly as they did before. And the only real problem with their looking as they did before is that they could look infinitely better, in ways that I will discuss.

But let me explain why you should care about these steps in the first place, why they are so much more than a mere instrument of ascent, a means by which museumgoers pass from street level into the building. Consider that the Upper East Side is remarkably devoid of eminent public spaces, with the obvious exception of Central Park. Consider as well that Manhattan — not to mention the outer boroughs — is peppered throughout with such public spaces. The Upper West Side alone has Columbus Circle, Lincoln Center, the grounds of the American Museum of Natural History, and Verdi Park (at 72nd Street and Broadway), among other spaces. And yet, if you think about it, the Upper East Side has only those steps in front of the Met.

But what steps. Go there on an average day, from April to October, when the weather is fair, and you will see as many as 500 human beings sitting on them as on a throne, contentedly watching the cars and people pass, or taking in such improvised street theater as the Afrobats, a trio of wise guys who show up near closing time and amaze the tourists with their feats of physical agility. Any number of movies have been shot on these steps, and I have it on good authority that they are a recurring backdrop for the series “Gossip Girl.” Simply put, there is no part of the Upper East Side that is as fully alive as the steps of the Metropolitan Museum on a fine spring day.

But not this spring, and perhaps not next spring either. Though roughly a third of the steps are still accessible, guards now discourage visitors from sitting on them while the museum is open. The result is a fascinating and object lesson in how urban spaces function. If you drive the homeless, or the criminal element, out of one neighborhood, they promptly move to another. But if you drive away the locals or tourists from a public gathering place, they usually just go home or back to their hotels. And that is why this most vibrant area of the Upper East Side now feels like a desolation, all its energy having been sapped and dissipated. A few souls collect around the two waterless fountains that flank the stairs, but the effect is nothing like what was there before.

And yet, the Met has been handed a golden opportunity to remedy the defects that have compromised the grandeur and efficiency of the entrance since it was created back in 1970. New Yorkers seem to have forgotten that the steps that Richard Morris Hunt originally designed for the museum, between 1894 and 1902, were far smaller than the ones we see today. In size and in the modesty of their ambitions, they resembled the narrow steps leading up to the Art Institute of Chicago, and they were flanked by a spacious but superfluous carriage path.

During the Hoving era, when the Met began to embrace an ever-expanding and increasingly populist audience for fine art, the museum wisely broadened the steps and thus transformed its entrance into one of New York’s finest public spaces. But the style in which the in-house firm of Kevin Roche John Dinkeloo and Associates designed the entrance some 40 years ago was entirely inapposite to the architectural legacy of Hunt, and of McKim, Mead, and White. Instead of a redolent classicism, the firm conceived the steps in an idiom of pared-down Modernism, using a tawny granite that was entirely out of sorts with the rest of the Fifth Avenue façade, not to mention that it was perilously slippery when wet. In one of the ironies of architectural history, however, the resolutely Modernist — and decidedly mediocre — firm of Roche, Dinkeloo was to develop, 20 years later, into one of the most proficient Neoclassical firms in the world, as they proved in the Met’s own Petrie Court and in its Greek and Roman Wing, which opened last year.

Both of these later spaces are superbly realized, and they hold the secret to how the steps should be redesigned. Let them be reclad in a paler, pinker stone that accords with the rest of the façade. Let the corners be classically curved rather than sharply angled in the postwar Modernist manner. Finally, let each step be furnished with a nosing, or slightly projecting rounded edge, such as you find in the grandest classical structures: the Capitol Building in Washington or any number of monuments in Rome.

That reconceived entranceway would be a monument and a memorial fully worthy of the tenure of the museum’s outgoing director, Philippe de Montebello. And there is still time to do it. But if the museum passes up this opportunity, in all likelihood it will not recur for another 50 years.