It stands to be New York City’s New Year’s Eve party of the century, or, at least, it took a century to happen.

The soiree is not at the symphony, or a dance club, or a celebrity’s penthouse, but deep beneath the street where a new subway will push off on its inaugural ride as the clock ticks down to midnight. With a sparkling toast, the new trains along Second Avenue on the East Side of Manhattan will carry an invitation-only group into the new year, including the track engineers, engineers, city bureaucrats and elected officials who worked on the subway over its long gestation. Cocktail attire is suggested.

“New Year’s Eve ushers in new beginnings, and this year, we will be celebrating the ambition and spirit of the New Yorkers who made the Second Avenue subway a reality and achieved what was once deemed impossible,” Gov. Andrew M. Cuomo said in an email. “There is nothing more New York than the subway, and I can’t think of a better place to celebrate this great New York moment.”

The agency that runs the city’s subway system is under the authority of the governor. For Mr. Cuomo, the opening of the subway by the end-of-the-year deadline is a moment worth boasting about. On Sunday, it will open to the public.