Okinawa Churaumi Aquarium in Japan - wow!

The main tank called the “Kuroshio Sea” holds 7,500-cubic meters (1,981,290 gallons) of water and features the world’s second largest acrylic glass panel, measuring 8.2 meters by 22.5 meters with a thickness of 60 centimeters. Whale sharks and manta rays are kept amongst many other fish species in the main tank.

http://jonrawlinson.com/2009/07/kuroshio-s...-shot-on-5dmk2/