On Tuesdays and Fridays, a quarter-mile stretch along the Landwehr Canal in Berlin's edgy southwestern neighborhood of Kreuzberg transforms into a vibrant hodgepodge of stalls peddling fresh produce and superb Turkish foods: savory gözleme flatbreads stuffed with spinach and cheese and griddled until dappled brown; golden rings of molasses-dipped simit bread flecked with sesame seeds; falafel sizzling in vats of hot oil; and tender meatballs known as köfte dürüm, simmered with peppers, tomatoes, and onions.