In 1999 The New World Mall in Bangkok caught fire and was abandoned. Then it got filled up by rainwater and started causing a mosquito problem. To solve this issue, local authorities decided to stock the waters with tilapia fish so they can eat these nasty insects.
Soon enough, the fishes filled the space and the mall became a new tourist attraction. Now you can enjoy the post-apocalyptic view and even buy some food to feed the fish.