What is the term for a covered passageway that often supports structures above ground?

The term "cryptoporticus" refers specifically to a covered passageway or corridor that is often used to support structures above ground. These structures are particularly characteristic of Roman architecture, where they provided a functional space for movement while also serving as a structural element in the architectural design, protecting activities from the elements and allowing for connectivity between different parts of a building or site.

In contrast, a via refers to a Roman road or street, typically used for transportation, while a portico is a roofed space supported by columns, usually at the entrance of a building, and does not necessarily function as a passageway for support. An atrium, on the other hand, is an open central courtyard found in Roman houses, serving as a reception area but not functioning as a covered passageway with structural support. Thus, "cryptoporticus" is distinctly defined by its dual role as a covered passage and a structural support, making it the correct answer.