Of all the aquariums in Japan, this is probably my favorite. One of the world's largest -- encompassing 26,570 sq. m (286,000 sq. ft.) and containing 2.9 million gallons of water -- it's constructed around the theme "Ring of Fire," which refers to the volcanic perimeter encircling the Pacific Ocean. Tours begin through a tunnel filled with reef fish, followed by an escalator ride to the eighth floor; from there, you'll pass through 15 different habitats ranging from arctic to tropical as you follow a spiraling corridor back to the ground floor, starting with the daylight world -- a Japanese forest -- above the ocean's surface and proceeding past Antarctica, Monterey Bay, the Great Barrier Reef, and other ecosystems as you travel to the depths of the ocean floor. The walls of the aquarium tank are constructed of huge acrylic glass sheets, making you feel as if you're immersed in the ocean. You'll see 30,000 specimens representing 580 species; stars of the show include whale sharks (the largest fish in captivity), Antarctic penguins, the odd-looking ocean sunfish (which has the circumference of a truck tire but is as flat as a pancake), and the Japan giant spider crab with its incredible 3m (9 3/4-ft.) span. English-spoken audio guides are available for rent for ¥300. Allow about 1 1/2 hours to tour the aquarium, avoiding weekends.