Bells clang. Auctioneers shout. Huge tuna fish cram a warehouse wall to wall.

This isn’t tuna from a can. It’s the real thing—and Japanese people take it very seriously. How much will a fish-lover pay for a tuna at the auction? Someone bids $38,000! And that price isn’t uncommon.

How many kinds of seafood can you think of? Tuna might top your list. Can you come up with five more kinds? How about 400?! More than 400 kinds of seafood come to the market from all over Japan and elsewhere. People at the market hunt for octopi, eels, and sea urchins—to name a few.

The market is the largest wholesale fish and seafood market in the world. A wholesale market sells large quantities of items to other sellers, who sell retail (directly to consumers). Since 1935, people have visited the market in the center of Tokyo, Japan’s biggest city. About 40,000 people used to visit the old market, called Tsukiji, every day. Businessmen came to the outskirts of the market on lunch breaks to buy a little bit of fish: noodles and raw-tuna bowls from retail stalls nearby. Meanwhile, other buyers spent big bucks on the auction floor for large amounts of wholesale fish.

This October, the market moved a mile and a half away to a place called Toyosu. Why? Japanese people are making room for the 2020 Olympics! Aging market buildings in Tsukiji will be knocked down and replaced with a parking lot for the Olympics. But not everyone agreed that moving the market was a good idea. Many people worried fish might become contaminated at the new location. People found a poison called arsenic in the soil and water there. So builders took extra steps for safety, using better water pumps and extra concrete to keep the poison away from the fish. Workers do not plan to drink the groundwater there or wash the fish in it.

Still, not everyone is convinced. The old market was quaint and full of history. The new one feels more like a factory. People could walk to the old market easily. They can reach the new market only by taking a train. Most nearby retail businesses moved to Toyosu too. But some sellers don’t want Tsukiji’s history to be lost. They say, “We’re not leaving!”