Several of Istanbul’s top fish restaurants are located some way from either Old City or Beyoglu, so that for the visitor there for lunch or dinner has the faint air of making a pilgrimage. rnrnIf you make the trek up to Poseidon, nestling in the affluent locale of Bebek, any doubt about whether the journey was worth it will be quickly smoothed away by maître d’ Mehmet Kahraman, who handles his customers – ranging from in-the-know tourists to Turkish celebrities – with considerable charm. rnrnThe outdoor terrace, which almost hangs over the Bosphorus, will impress just as much, and last, but certainly not least, is the fish, super fresh, as one would expect, and prepared with consummate skill. A superb restaurant. Book in advance.