Manhole covers are heavy, circular lids that cover openings to underground utility systems, such as sewers, water lines, and electric cables. They are designed to keep people and animals safe while allowing access for maintenance workers. Typically made of cast iron or steel, these covers are strong enough to support the weight of vehicles. The design of manhole covers often includes a raised pattern to provide grip and prevent slipping. They are usually round because this shape cannot fall through the opening, making them safer than other shapes. Manhole covers are essential for urban infrastructure and maintenance.