Most natural rivers flow along the surface of the land, there are also those that are underground. They carry water through grottos, caves, and make their way through rocks (usually in soft sedimentary limestones, dolomites, and sandstones). There are watercourses whose path only partially passes through the kingdom of Hades. But does it happen that an underground river flows under a surface river, is there a relationship between them?

Most natural rivers flow along the surface of the land, there are also those that are underground. They carry water through grottos, caves, and make their way through rocks (usually in soft sedimentary limestones, dolomites, and sandstones). There are watercourses whose path only partially passes through the kingdom of Hades. But does it happen that an underground river flows under a surface river, is there a relationship between them?