Underwater cities are urban areas built beneath the surface of oceans or large bodies of water. These innovative structures aim to provide living and working spaces while addressing challenges like overpopulation and rising sea levels. They often incorporate advanced technology and sustainable practices to create a self-sufficient environment. Designs for underwater cities include transparent domes and tunnels made from durable materials, allowing natural light to enter. Concepts like Ocean Spiral and Seascraper showcase how these cities could function, featuring residential areas, parks, and even farms, all while preserving marine ecosystems and promoting exploration of the underwater world.