Other far-fetched ideas are hair-raising. A 1924 issue of Popular Science included a plan to reduce traffic and create more parking spaces by filling in and paving over the East River. A decade later, Modern Mechanix had a similar plan for the Hudson. In the early ’60s, Buckminster Fuller, Shoji Sadao and June Jordan proposed to double Harlem’s housing stock with 15 massive piles, raised on top of existing buildings, that would have looked like cooling towers from some Brobdingnagian nuclear power plant.

But over all, whether or not any particular lost ambition is to one’s taste, the more singular it is — the more completely it expresses a totalizing aesthetic vision like that of Wright or Fuller or Robert Moses — the more incongruous it looks against the noisy background of everyone else’s. (In this way the exhibition designer Christian Wassmann’s busy hanging is true to its material.)

The unfinished fantasy of New York City, this reminds us all, is of a thousand competing ideas canceling one another out — with envy, greed, destruction and lethargy — and arriving half by accident at a complicated compromise that everyone can more or less live with, and even come to love.

In 1964, on the occasion of the World’s Fair, hundreds of workers replicated every one of the city’s nearly 900,000 buildings in miniature, combining them into what became the unforgettable centerpiece of the Queens Museum’s permanent collection, the 9,335-square-foot panorama of the City of New York.

This year, a small team of Columbia architecture students, under the direction of Joshua Jordan, made glowing white models of a number of this show’s forgotten projects to add on to that panorama. Not one but two tall monoliths now overlook the harbor: William Zeckendorf’s rooftop airport covers a substantial fraction of Manhattan’s western edge, and I.M. Pei’s pinch-waisted hyperboloid rises a hundred stories above Grand Central Terminal.