One of the most popular activities in New York on Christmas Day is visiting the Rockefeller Center. This iconic landmark is home to the famous Christmas tree, which is decorated with thousands of lights and topped with a star. You can also explore the various shops, restaurants, and attractions in the area. Additionally, you can visit the nearby Museum of Modern Art or take a walk through Central Park, which is always a beautiful sight during the holiday season. You could also visit the Statue of Liberty, where you can take a tour and learn about the history of this iconic landmark.