Gigantic ice sculptures (basically an entire town built of ice) and lit with neon lights during nighttime. Plus an exhibition of snow sculptures.

It's a bit confusing, as there are different places with different names:
1. Harbin Ice and Snow World = Large Ice Sculpture Buildings (north of the city, west of the big road)
2. Sun Island Park = Snow Sculptures (north of the city, east of the big road)
3. Zhaolin Park = Small ice sculptures and a few copycat buildings (in the city)

I placed the location indicator on the map where you have to leave the big road north of town.

1&2 are a must-see experience. Visit the snow sculptures during daytime (bright sunlight is best to take pictures) and the ice sculptures at night (when colorfully lit).

The exhibition in Zhaolin park (#3) contains some small ice sculptures from competing international teams (like cristal carvings 2x2m) but is hardly worth the money unless you're an art appreciator.

Note that a cab back at 10pm from the Ice World will cost you 50-80 Yuan instead of the regular 15-20. Take the bus instead for 2 Yuan which will take you across the river to the end of the bridge from where you will be able to take a cab at a regular rate. Same goes for
Sun Island Park at 5pm (closing time) except that there you can walk across the river back to town.