The Arc de Triomphe is the Paris landmark at which the city's New Year's Eve celebrations traditionally center on the Champs-Élysées.
The monument stands at the western end of the avenue, at the center of the Place Charles de Gaulle. On New Year's Eve, crowds gather along the Champs-Élysées, while the monument is commonly used as the visual focus for light projections, fireworks, or countdown imagery. The Eiffel Tower is also illuminated during major Paris celebrations, but it is not the landmark named in this question.
Napoleon commissioned the Arc de Triomphe after the French victory at Austerlitz in 1805. Jean Chalgrin designed it, and the monument was inaugurated in 1836, during the reign of King Louis-Philippe. Its reliefs commemorate French military achievements, and the Tomb of the Unknown Soldier lies beneath it.
The avenue's celebrations can be extremely crowded, and arrangements vary from year to year. The monument's historical role, rather than a permanent annual fireworks program, explains why it remains the best-known focal point.