The mall ceased operations over 20 years ago, and subsequent floods turned the site into an ideal breeding ground for marauding mosquitos. To combat this, local shopkeeps started tossing in koi, carp, tilapia, and catfish. But the fish began thriving as well as the mosquitoes, mainly thanks to all the tourists who started showing up to feed them. Since no one thought to send crocodiles to eat the fish, and then hippos to eat the crocodiles, the place became a makeshift aquarium.
In 2015, authorities finally decided that that having an unlicensed aquarium / biohazard / structural menace smack dab in the middle of the city was no longer acceptable. But don't worry, before the entire structure was demolished, the fish were relocated to waterways elsewhere in the country. There, they are presumably shunned and ostracized by the other fish, who cannot believe or even fathom the concept of a mall.