Manhole cover.
Manhole covers are removable plates that form the lid over the opening of a manhole, which is an access point to underground utilities like sewers, water lines, or electrical cables.
They are designed to provide access for maintenance and inspection while also keeping people and debris out of the underground spaces.
This specific cover is made of a composite material, indicated by the "RESINTUFF" branding, which suggests it's a durable and strong alternative to traditional cast iron covers.