The world’s first large-scale cultivation of living coral is in a tank that has no roof, allowing natural sunlight in through the top. This feature allows for a thriving coral reef and a stunning display for visitors to Japan's most impressive aquarium, on the island of Okinawa.

The Okinawa Churaumi Aquarium was the largest in the world when it first opened in 2002 on the former grounds of the 1975 World’s Fair in Ocean Expo Park. The main tank holds nearly 2 million gallons of water, making it the third largest in the world today (behind the Georgia Aquarium and Dubai Mall Aquarium).  It is one of few that keeps and raises whale sharks and breeds some of the largest species of manta rays. In total, it is home to more than 26,000 creatures from 750 species. There are 80 different species of coral alone, which fish in the coral tank help protect from seaweed and sea anemones that might hinder its growth. 

What makes the aquarium extra unique is its deep sea exhibit with creatures like flame snappers, black snoek, and bioluminescent shrimp, creatures that are difficult to raise in captivity because they usually live between 200 and 700 meters below the ocean surface. The massive Kuroshio Sea Tank is one of 77 tanks in the aquarium and among the largest in the world. Its half-dome design at the bottom allows visitors to walk through it, giving the feel that you're viewing whale sharks, rays, and other creatures of the deep from the ocean floor. 

The water for the saltwater exhibits, including the Kuroshio Tank, which is named after a warm current off the coast of Okinawa, is pumped in from a part of the Okinawa Sea off the shore. This helps the aquarium imitate the natural conditions of the surrounding sea, a mission somewhat echoed in its name, "Churaumi," which translates from the Okinawan dialect as “clear, beautiful sea.”