A new event this year was the Tokyo Millenario (official site), located near JR Tokyo Station, Marunouchi side. The Millenario hosted crowds of hundreds of thousands of people. The day we went (December 26th), we had to wait in line for over an hour to see the Millenario.
What is a Millenario? It's a giant Christmas display in the form of lighted gateways. According to the material being handed out, it originally came from Spain. Kobe City was the first to sponsor a Millenario for the year 2000 New Year's. Tokyo's Millenario was smaller but just as jam-packed. The display is being held December 24,2004 -January 1, 2005.