"Design a futuristic, sustainable city with a population of 2 million people, located in a circular, radiocentric layout. At the heart of the city, there is a large, monumental central building serving as the core of government, business, and transportation. The city is organized into five concentric rings, each with its own purpose and character. The first ring around the center houses high-density residential buildings, commercial areas, hospitals, and educational institutions. The second and third rings are residential areas with medium-density buildings, parks, and local markets, offering everything residents need within walking distance. The outer two rings feature low-density, family-oriented housing, vast green spaces, and smaller commercial hubs. All transportation is electric, autonomous, and public, with no private cars allowed. Include an advanced, futuristic underground metro system connecting all the districts, visible in the image with metro stations in the central building and beneath the city, with sleek, modern trains. The city has extensive pedestrian paths and bike lanes. The buildings are eco-friendly, with solar panels, green roofs, and vertical gardens. The entire city is surrounded by lush, green parks and nature reserves. There are vibrant, large public squares in every district, with modern, eco-conscious architecture, advanced urban planning, and integrated natural spaces."