Ildefons Cerdà was a Spanish urban planner and engineer, best known for his work in the mid-19th century. He is most famous for designing the expansion of Barcelona, known as the Cerdà Plan, which aimed to modernize the city and improve living conditions. His plan introduced a grid layout with wide streets and green spaces, promoting better air circulation and sunlight. Cerdà's vision was not only focused on aesthetics but also on social reform. He believed that urban planning could enhance the quality of life for residents, addressing issues like overcrowding and sanitation. His ideas have influenced modern urban planning practices worldwide.