The most amazing place in the world is the Tsukiji fish market (pronounced SKEE-jee) in Tokyo: a covered market with hundreds and hundreds of wholesale fish vendors. Buckets of live eels, guys cutting up frozen tunas with band saws, squid and octopus, endless endless sea creatures over many acres. The guidebook says that the highlight is the morning auctions at 5am, but I didn't manage to get there that early. There are also hundreds of vendors of diverse sorts (not just fish) in the public areas outside. Others here have mentioned the sushi bars in particular. I have to say that my three sushi experiences at Tsukiji weren't that great, and one was remarkably poor. (I didn't take down the names of the places.) I did, though, have a terrific breakfast at a tiny counter in the outermost row of shops where a cook keeps a cauldron of tripe stew in a rich brown sauce. Although the place has a fair number of tourists, the guy found it hard to believe that I wanted to eat his stew, and he pointed at his stomach to make sure I understood what it was. In fact it was the best thing I ate in a week in Tokyo.