Babylon is traditionally associated with the earliest recorded New Year's festival, Akitu.
Akitu was a Mesopotamian religious festival connected with the renewal of kingship, the agricultural cycle, and the worship of the god Marduk. In Babylon, the principal observances took place in the month of Nisanu, which began around the spring equinox rather than on January 1.
The festival included processions, rituals, and the public affirmation of the king's relationship with the gods. A major part of the ceremony involved the movement between Babylon's temple complex and the Akitu house outside the city.
Calling Babylon the site of the “first New Year's celebration” needs care: surviving evidence records ancient year-renewal festivals, not a single universally accepted first celebration in the modern sense. Akitu is nevertheless the standard historical example cited for an early documented New Year's festival.