IT was two years ago, in June 2005, that residents of the Upper West Side got their first glimpse of the two glass-sheathed towers that were to rise on Broadway at 99th Street. The local community board was having its monthly land use meeting — not generally an occasion of high drama — and Gary Barnett, president of the Extell Development Company, came to share renderings of his proposed buildings. As he unveiled them, a gasp was heard throughout the room. “People shrieked,” recalls Sheldon Fine, chairman of Community Board 7.

Mr. Barnett had spent millions of dollars acquiring air rights from properties next to his own lots on the east and west sides of Broadway. These air rights, as the neighborhood came to learn, allowed him to build hundreds of feet higher than the 16-story ceiling that defines much of Broadway above 96th Street.

For those who still didn’t grasp Mr. Barnett’s intentions, the name he gave his towers was a hint: Ariel East and Ariel West. According to Mr. Barnett, the name Ariel was borrowed from a star. In fact, the only celestial body commonly known by that name is one of the moons of the planet Uranus, but the message was clear. Mr. Barnett aimed high.

Not since Donald Trump’s Riverside South project in the early 1990s, said Mr. Fine, has a set of buildings on the Upper West Side aroused as much opposition as Mr. Barnett’s towers. Petitions circulated, gathering signatures by the thousands. Demonstrators took to the streets. None of this, however, did anything to stop the towers. Floor by floor they rose, plywood forms giving way to rebar and concrete, and finally to acres of glass. Residents will begin moving into Ariel East in September and into Ariel West later in the year.