konnichi wa こんにちは

Having lived in Sapporo off and on since 1991, as an exchange student, as well as working there previously, i can safely say sapporo is my favorite city in all of japan. I suppose i am biased because my Japanese host family of more then 15 years is all there. But it also has such a lovely feel. It's not great to go to if you're new to visiting japan and want to see the stereotypical historical castles and ancient sites of Nara, Kyoto, and Osaka. I highly recommend those places for sight seeing on honshu. But sapporo has charm of its own. It's a large city with lots of interesting things to do, a beautiful park, Odori Koen, great clock tour for look out views, and best of all there's not the mainland humidity in summer time. The flowers and parks are gorgeous! Sapporo is well known for its amazing fresh cuisine. Miso Ramen is not to be missed! There are many beautiful Onsen hot springs hotels in Noboribetsu as well. Hokkaido is also known for it's amazing wildlife. Little known is most of japan's food is grown here, so there's lots of wide open nature spaces. 

If snow is your thing, Niseko boasts amazing powder, and is a cute little town. The winter Olympics were held in Sapporo in the 70's and you can visit the ski jump for a view overlooking the entire city. winter sports are very popular here...skiing, snowboarding ect. There is also the Sapporo snow festival with huge snow sculptures in february that people come from around the world to see. 
If you're traveling with kids, the maruyama zoo is great, as is the acquarium. I've taken my own children to visit without problems.
whatever your dream about japan is, if you can squeeze a trip to Hokkaido in, i think Japan isn't complete without this journey. The people are incredibly kind, and helpful. It's the best of both a large city, and the countryside combined. Safe travels!