What is a circular to elliptical closed depression in karst areas?

A circular to elliptical closed depression in karst areas, often referred to as a "sinkhole" or "doline," is a geologic feature formed by the dissolution of soluble bedrock, such as limestone, due to acidic water. This process creates a depression in the landscape as the ground collapses into an underground cavity. These depressions can vary in size and depth and are characteristic of karst topography, which is marked by features like caves, springs, and underground rivers. They can pose hazards to infrastructure and ecosystems, as well as provide unique habitats.