Copenhagen is the Danish city known for a New Year's Eve fireworks tradition at Tivoli Gardens.
Tivoli Gardens is an amusement park in central Copenhagen, Denmark, and it traditionally marks New Year’s Eve with festive decorations, entertainment, and fireworks. The park opened in 1843 and became one of Copenhagen’s most prominent cultural and recreational landmarks. Its seasonal atmosphere combines rides, gardens, restaurants, concerts, and holiday events.
Tivoli is sometimes confused with Denmark’s nationwide New Year customs, such as breaking old dishes or jumping from a chair at midnight. Those practices are not unique to Tivoli Gardens and do not identify the city. Copenhagen’s association with the park is the key geographic fact: Tivoli lies near Copenhagen Central Station and Copenhagen City Hall Square. New Year celebrations elsewhere in Denmark may also include fireworks, but the landmark named in this question is specifically the historic Copenhagen amusement park.