What a beautiful sight, and for all to enjoy. 
 
In most cities, drainage canals are the last place you’d expect wildlife to thrive. However, in the city of Shimabara on Japan’s Kyushu island, the street’s gutters are so clean they are home to hundreds of koi carp. The unusual fish habitat is a product of the volcanic activities of Mount Unzen that resulted in the 1792 earthquake and tsunami. The tragic natural disaster killed 15,000 people, but it also triggered an abundance of fresh water springs. Clean water began to flow through the city’s drainage channels; so in 1978, authorities decided to release colorful koi into the 100-meter-long waterway.
 
Hundreds of Koi Fish Happily Swim in This Japanese City's Drain Channels (mymodernmet.com)