A mall or Aquarium.

In Bangkok, A 11 story mall was build in 1980s. The mall was famous in its initial days but it was found violating laws. And after fire it was left abandoned for years.
With the passage of time rainfalls causes filling building with water gradually. The area was now under the attack of mosquitos. Rather than using sprays and other pesticides, People give a unique idea.

Freshwater fish were putted in the water to eat the insects. You can hear the voice of fishes splashing in the water even if you are near the building. People are not allowed to though wastes in it.

Here are some photos:

via Daily mail.