Tokyo is ablaze with Christmas illumination at this time of the year. One of the most famous ones is the area around Roppongi Hills. The ones along Keyakizaka-dori (road towards Azabu-Juban) are especially nice. It got off rather early on November 5th and will last till December 25th.
The trees near the main entrance (66 Plaza) will also be lit with red and auburn lights. Also, a small pond and garden (Mouri Teien) near the arena will be decorated. Definitely worth a look.
When: Until December 25
Where: Roppongi Hills and surrounding areas
Time: 17:00-23:00 (Mouri Teien and Keyakizaka-dori)/ 17:00-24:00 66 Plaza