Which city is characterized by a layout that includes diagonal streets overlaying a gridiron pattern?

The city characterized by a layout that includes diagonal streets overlaying a gridiron pattern is Washington, DC. This design was largely influenced by Pierre Charles L'Enfant, who was commissioned to create a plan for the city in the late 18th century. He envisioned a grand and functional capital that featured wide avenues and diagonal intersections, which would connect key government buildings and monuments. This design not only improved traffic flow but also enhanced the visual appeal of the city, creating significant sightlines and open spaces.

The incorporation of the gridiron pattern can also be observed in various parts of the city's layout, with major streets running in a north-south and east-west direction, providing structure while allowing for the diagonal streets to facilitate movement and access to important sites. This unique combination of planning elements makes Washington, DC, stand out from other cities with simpler grid layouts or less intentional street designs.