Final answer:
A lintel is the structural element located over a fireplace opening that supports the masonry above. Made of stone or brick, it can be supported by engaged columns or colonettes and is a part of larger structures like entablatures in classical architecture.
Step-by-step explanation:
The structure located over the fireplace opening that supports the masonry above is known as a lintel. This architectural feature often takes the form of a horizontal beam and is integral to the stability and integrity of the surrounding structures. Lintels can be made from various materials, such as stone or brick, and are supported by the elements on either side, like engaged columns or colonettes.
In historical contexts, from ancient Greek temples to Mycenaean citadels, lintels were part of the larger structure known as an entablature, which included the frieze and architrave. The use of the lintel is not only functional but can also incorporate decorative aspects, such as intricate carvings or the integration with other masonry work like friezes or inscriptions.