Sun Island or Ice and Snow World? I think they're both part of the Harbin Ice and Snow Festival.

Yes, they are both part of the festival. Seen from the map, the Ice and Snow World is in the west of the Sun Island, 2 miles west of the Sun Island Scenic Area. If you have enough time, it is suggested you visit both of them. Or, you may only visit the Ice and Snow World for it boasts numerous fabulous ice and snow sculpures.

Merci beaucoup. So the Ice and Snow World usually has more ice sculptures that look like buildings around the world?

Yes, you are right. That theme park is famous for having this kinds of sculptures. You can enjoy your time there. :)