Step 1: Understanding the Concept:
The question asks to identify the urban planner responsible for the large-scale renovation of Paris in the 19th century, which created its famous boulevards.
Step 2: Detailed Explanation:
The comprehensive urban renewal of Paris was commissioned by Emperor Napoleon III and carried out between 1853 and 1870 by his prefect of the Seine, Baron Georges-Eugène Haussmann. This massive project, known as Haussmann's renovation of Paris, involved demolishing medieval neighborhoods and constructing wide avenues, parks, and squares, as well as new sewers, fountains, and aqueducts. This is what gave Paris its modern and iconic layout.
Step 3: Final Answer:
Baron Haussmann planned the main streets of modern Paris.