Not sure on the rating as the second largest in the world, but that is an impressive tank.
The Georgia Aquarium in Atlanta has a 6.3 million gallon tank (about 3X the size of the OP) and has the 2d largest aquarium viewing window in the world. It is a site to behold. If you are ever traveling through Atlanta, I highly recommend this stop. The tickets are a little pricey and the place is always packed... but the main exhibit alone (called ocean voyager) is an amazing experience... you walk through a 100 ft long tunnel which is made of acrylic and underwater, and then come upon the main viewing window which is 21'X63'. It is truly amazing.
Here is a crappy photo I took of it... It is about twice as wide as the image shows, but you get the idea of the scale...