On June 15, there will be a great event in Jogja, called Snow International with a theme "Bersalju di Jogja" (Snowy in Jogja) which will be held in Saphir Square. Great, since finally i have a good reason to go to Saphir (believe it or not, i haven't been to Saphir ever, even though i have been in Jogja for about one month after i came back from Jakarta).
The grand opening will be on 10 - 11 AM and after that, it will be open for public. There will be a lot of ice craft and it's being crafted by seven famous ice crafter and became the world champion. The room temperature will be kept for -15 degrees to preserve the ice. This event will last for about two months, so you still had a lot of chance to see this event (just plan to go to Jogja in weekend).
I'm planning to go there and have a nice photo session (i don't know whether it's allowed or not, but we will see in the next few days). Just wait and see
Reference : Kedaulatan Rakyat