Sapporo and Niseko
Two winter trips to Sapporo, Hokkaido has made one thing clear: It's not just another Japanese city. The foreign influence is quite visible just by looking at the western-style, block layout of the city. Other Japanese cities tend to have a lot of winding streets and narrow alleys that you randomly wander down. Add to that the icy slick and snow galore during the winter, and it's a different Japan.
The Sapporo Snow Festival is a main attraction during winter, and it's worth checking out. Ice sculptures and food stalls line the streets in between more gigantic ice sculptures, some of which serve as stages for concerts and performances. There's also a ramp in the streets where snowboarders are jumping of and performing aerial tricks.
If you're a ski or snowboard fan, heading a couple hours outside the city to Niseko is well worth your while. It's a well done ski resort - not quite as upscale and fancy as some others, but the facilities, runs and snow itself are great. Powder.
Do check out some food in Sapporo as it's a tweak on what many know about. Due to the cold environment, foods like their ramen tend to be rich and hearty. Their ramen style is a heavier, miso broth, thick noodles, various seafoods and corn with a slice of butter on top. The cold climate also leads to excellent seafood, but yakiniku BBQ is also a big deal. When it's time to get your grill on, lamb is the meat of choice here.