This surprisingly-large aquarium is busy 365 days a year with visiting groups of students and a mix of Japanese and international tourists. It's famous for being the largest aquarium in the world and it's full of sea creatures that are as interesting as they are bizarre. If you're visiting Osaka, it's worth spending one morning here checking out the enormous sharks, crabs with 6-foot long legs, hypnotic jellyfish, or the world's largest rodent (it's terrifyingly big!). It was pretty incredible! My only tip is to have patience with the crowds: it's a common occurrence throughout Japan.