If Haeundae and Gwangalli are Busan's sea, Jagalchi and Gukje are Busan's city. Half a day in the old centre shows you a completely different place from the beaches.
Jagalchi Market — pick it and they cook it
Busan's signature fish market. What sets it apart is the arrangement: you choose the fresh seafood yourself and an eatery inside the market cooks it on the spot.
You are not ordering from a menu, you are choosing from a tank and going upstairs to eat it — so on a first visit, ask the price before you point.
Gukje Market — every alley is its own thing
The setting of the film "Ode to My Father". With everything-shops and old snack stalls down every alley, it rewards walking without a destination rather than aiming for one shop.
Adjacent BIFF Square is where you eat the street food — hotteok and fish cake.
Have the fish cake on a skewer
Busan fish cake is famous across Korea. Skip the packaged version and have it hot on a skewer where it is made — inside the market or at BIFF Square.
Add the coast and it becomes two days
Attach Haeundae or Gwangalli to this half day and you have a natural one-night trip: the traditional and the modern sides of the city, joined.
Each coastal half is covered separately, because Haeundae is governed by a walking route and Gwangalli by the hour the bridge lights up.
Market-by-market detail and what to eat is on the WeBring blog.