In december of Taiwan, what are the things to see for traveling?

It will be a little bit cool at that time. The average temperature is about 17.2 C around Taipei, 17.7 C around Taichunag and 18.8 C around Tainan. December is the rainy season in Taiwan, so you had better not to go to the mountain areas in Taiwan. You can choose to go go some attractive spots in Taipei such as Maokong, Shilin Night Market or Presidential palace. If you want to see the snow in Taiwan, you can choose to go the Snow Mountain.