Osaka, the largest city in West Japan, is a powerful place no matter when you visit it. It's the home of Japan comedy, and with all the takoyaki, okonomiyaki and other inexpensive, delicious "flavors of the common people," it's only natural that it also gets called an "eat till you drop" town.
The city's symbols are on the one hand the mighty donjon of Osaka Castle, and on the other hand the downtown landmark Tsutenkaku. The Tower of the Sun built by artist Taro Okamoto at the venue of Expo '70 held in 1970 is also very popular.
The bay area also has some world-class sightseeing spots, such as Universal Studios Japan and an aquarium with gigantic whale sharks.