A skyline is the outline or shape of a city or landscape as seen against the sky. It is often defined by the tallest buildings, towers, and natural features like mountains. Skylines can vary greatly depending on the architecture and geography of an area, making each one unique. Cities like New York and Chicago are famous for their distinctive skylines, which are often photographed and admired. Skylines can change over time due to new construction or urban development, reflecting the growth and evolution of a city. They serve as a visual representation of a city's identity and character.