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In the middle of West 69th Street between Central Park West and Columbus Avenue, behind some scaffolding and a green wooden wall, stand a few precarious inches of facade. It is a Potemkin-like sop to local landmark laws, all that remains of two brownstones from an earlier Gilded Age that were leveled unceremoniously last summer.

A few years from now, this remnant will be grafted onto a mansion that may well cost $100 million by the time it’s finally finished. But for now, all they’re doing is digging.

Every morning at 8 o’clock sharp, the jackhammering begins. All day long the drilling and banging and beeping go on. Only on weekends and the holidays of the politically potent — Christmas and Rosh Hashana, for example, but not Martin Luther King’s Birthday — does it cease. It was supposed to end last December, then in February, then this month. Now, they say, it could last all summer.

Manhattan has countless monuments to outrageous wealth, most recently and glaringly the $238 million penthouse that the hedge fund billionaire Ken Griffin just bought at 220 Central Park South. Lacking famous owners, a prestige address, a brand-name architect or coverage in tabloid real estate blotters, 48-50 West 69th Street has thus far been a study in inconspicuous consumption. But it reflects extravagance of a different sort.