Tsukiji Fish Market
Thousand of wholesalers and buyers broker deals in this chaotic market. Tourists are banned from the early morning tuna auction but can wander through the market after 9 a.m. when business is winding down. It's every man for himself as fish is moved from seller to buyer in fast-moving electric carts; they zip around, dodging obstacles (i.e. people) at break-neck speed.
Moe will blog more about the market, I think.