Satoland Sapporo is one of the 3 sites for the Sapporo Snow Festival, with Odori Park and Susukino being the other two. Satoland is a little far from the city, but can easily be accessed during the snow festival by free shuttle buses that run from the other sites. While most of the impressive sculptures are at the Odori Park site, Satoland has such things as an ice labyrinth (maze), huge ice slide, ice rafting (a raft gets pulled by a snow mobile) and even hot air balloon rides weather permitting.
For more information and a few photos, see the official Satoland Site.
Thanks to Greg Logan for the photos!