You glance toward Lower Manhattan and expect to see a single tower where two once stood. You delight in the spectacle of sunlight glinting off its slivered facade.

Suddenly, you realize, the new 1 World Trade Center — the Freedom Tower — has become familiar.

And 15 years after the twin towers disappeared abruptly from the skyline, they have begun to fade from popular consciousness.

They once nearly rivaled the Statue of Liberty and the Empire State Building as simple, graphic representations of the complex idea of New York. In movies and logotypes, on knickknacks and letterheads, two parallel strokes meant only one thing. Now, a shaft of slender, alternating isosceles triangles — so simple a child could draw it — is coming to mean the same thing.

Campagna & Sons of Brooklyn, which makes boxes for pizzerias around Lower Manhattan and nearby New Jersey cities like Hoboken and Weehawken, carries a Freedom Tower design, in 10-, 12-, 14-, 16- and 18-inch sizes. Instagram currently counts nearly 200,000 posts tagged #oneworldtradecenter. Fishs Eddy, an imaginative housewares store in the Flatiron neighborhood of Manhattan, has introduced the new 1 World Trade Center to its popular “212” line.