The good news is that a stunning building has just arisen in New York. The bad news is that, one week hence, it will have vanished without a trace. More than that, the forces behind the structure – uniquely among living things in the five boroughs – actually seem to be trying to suppress any publicity that might ordinarily accrue to them, for fear that more people will show up at their doorstep than they can handle.

That said, it is hard to hide a building as large and conspicuous as the Parthenon, especially the one that has just alighted on the makeshift acropolis of the Rumsey Playground, which beetles over the bandshell in Central Park. The occasion for this structure, whose summit puts one in mind of the cornice of the Parthenon, is a fashion show to be held by H&M over the next few days.

To those of a somewhat literal or unimaginative turn, the whole thing, designed by the public relations firm KDC, could be described as a glorified tent. But it is far more than that. Its skeletal structure is composed of steel girders as strong as those in most skyscrapers. These are clad in white cloth along the sides, while transparent sheets of plastic serve as roofing. Over the sandy base of the playground, two raised levels serve as seating for the fashion show. A complex set of lights can be cranked up along metallic gurneys.

If the dome of high pressure persists over the city as it has for the past week, the inhabitants of this most temporary of structures will be treated to a dazzling view of the peerless blue sky. Shelley had a word for it: “hupaithric,” which he stole from Aeschylus of Athens. It means “dwelling beneath the sky” but also reveling in and embracing the expansive skyness of the sky. And it seems appropriate (well, almost) to the temple typology of the H&M building, whose elegant boundaries seem to harness heaven itself.

This building brings to mind Shigeru Ban’s Nomadic Museum, which recently went up by Pier 54 and the Westside Highway, where it will remain for a few more months. But that structure, its walls formed from stacked shipping containers, seems ploddingly permanent next to the H&M temple. Suddenly you realize that Mr. Ban’s building, for all its impermanence, is much more solid and stolid than it ever needed to be – it is an act of overkill, and not an especially lovely one either. The H&M temple, by contrast, is in every sense nobler and more economical.

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A quarter of a mile to the south, but still in Central Park, stands the luckless entrance pavilion to the Heckscher Playground. Last week, its roof burst into flames, and the efforts of the firefighters to put out the conflagration were greatly impeded by the fact that the nearest hydrants were not in service.

The building, which dates from 1926 and now houses a pair of bathrooms and a storage shed for the parks department, was about to be renovated in any case. And the fire, though dramatic, caused little permanent damage. But it turns out this little building is far more interesting than most people ever realized.

I have been aware of it all my life, going back to the days when I played in its shadow. And for some years now, I have been intrigued by its chaste classicism. Surely it is no great shakes as a building; even its classical motifs are rather pallid. But is it not delightful that there was a time, before Robert Moses, when public bathrooms in Central Park were adorned with ionic columns and pilasters and arrayed as two pavilions on either side of a columned portico?

Now Sarah Cedar Miller, the Central Park Conservancy’s official historian, has brought to light an astonishing fact: This little architectural folly was among the final efforts of the architects Carrere & Hastings. Conceive that one of the most illustrious firms of the gilded age, a team responsible for the Frick residence and the library on 42nd Street – not to mention 20 other noble buildings in Manhattan – should have deigned to create a pavilion and bathrooms for a playground in Central Park!

While the firm’s two most famous projects were in the spirit of the French Baroque, the dominant aesthetic here is that of the Queen Anne style and of Hampton Court, with bright, white classical details set against a red-brick ground. In typical ly bad taste, however, Robert Moses doubled the building in the early 1930s, plugged up the portico, and turned the whole thing into a storage shed whose once-flat roof was now capped with a pair of hipped mansards. Worst of all, as the playground grew around the structure, it lost its function and meaning as a grand entrance.

Part of the Conservancy’s complete overhaul of the playground will be to reopen the columned portico. The hipped roof will be slightly enlarged however, to make up for the space lost when the portico is resurrected. At that point, one of the final projects of Carrere & Hastings will be restored to its original function, as the grand entrance to the Heckscher Playground, the first of many that were built in Central Park.

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The Ukrainian Museum has just moved to 222 E. 6th Street in the heart of Ukrainian New York, from the townhouse where it resided since the 1970s. Now, for the first time, it inhabits an imposing structure built specifically for the museum. Designed by George Y. Sawicki, the structure is pinkishly postmodern, and the fortress like masonry of its facade may hold some vernacular meaning for Ukrainians that is lost on the rest of us. The stylish expanse of finished brick rises above a tripartite, glass-and-steel entrance, flanked on either side by paired pilasters delineated in white stone. Inside is a spacious and well-lit sequence of galleries, with pale, maple floors and doorways. The museum’s initial exhibition, of the sculptures of Alexander Archipenko, is impressively serious and scholarly.