The fanum is a type of Celtic temple, most frequently found in Britain and Gaul, that features a cella (inner chamber) surrounded by an ambulatory for conducting deiseal. They are best typified by stone structures often built over originally Celtic religious sites in the Roman period. Their plan grew out of the ritual architecture of earlier Celtic sanctuaries.
“Classic” refers here to a plan that includes all of the elements of the fanum genre without any hybridization. I.e., a single, approximately equilateral cella tower is surrounded by a built ambulatory, but without Mediterranean layouts such as the pronaos.
Easily the most common type. Quadrangular fana are rectangular structures that are either square, or nearly-so. The ambulatory area is typically about twice that of the cella.
These fana are roughly equilateral (round) polygonal shapes, with varying numbers of sides (e.g. octagonal, decagonal, hexadecagonal, etc.)
These are fana with circular (or nearly-so) cellae, but which typically have polygonal ambulatories.
These are fana which have two cellae joined with an ambulatory.
This category reflects cultic buildings that are an equilateral cella with no built ambulatory.
This category is where an open courtyard exists in lieu of the cella structure. In other words, a built ambulatory alone.
This category is where the cella is joined in height and roofing to the ambulatory, rather than being a taller-standing tower with separated roof.
These are Romano-Celtic temples which have fanum-like features (e.g., the ambulatory) incorporated, but which also exhibit Mediterranean layout characteristics not found in Classic fana or indigenous Celtic shrines. Examples include elongated rectangular plans, or being opened by a pronaos.