Something very interesting in Istanbul is that there are some boats where people grill fish inside, and make sandwiches that are sold right away. Cooking fish on a boat like a grill-boat. These boats can be found just after the Galata Tower in Eminönü district which is a main tourist destination in Istanbul.
Each fish sandwich contains a bit of lettuce and onions also fresh lemon juice and salt. The price for a sandwich is of 4 Turkish Liras. You can sit and eat your meal in the tables and ask for a drink, or, you can just take away. This is a nice trip to eat cheap in Istanbul and to escape other expensive restaurants around the city.
