Step 1: A gridiron street pattern is a city planning method where streets form a grid, meeting at right angles. This layout is generally employed to enhance navigation and order.
\n\nStep 2: Chandigarh, an Indian city, was designed by architects Pierre Jeanneret and Le Corbusier using a gridiron layout to support its urbanization.
\n\nStep 3: Philadelphia, in the United States, also features a gridiron street pattern, established during its 17th-century planning.
\n\nStep 4: Cairo and Venice do not employ gridiron street patterns. Cairo's streets exhibit a more organic, less structured layout, while Venice is characterized by its intricate network of narrow streets and canals.
\n\nConclusion: Chandigarh and Philadelphia are cities that utilize a gridiron street pattern.