narthex of the basilica of san vitale /originally, the octagonal plan was preceded by a quadriporch, lost over time. the forceps-shaped narthex remained, and is placed tangentially to an edge of the central plan, instead of being placed in axis with the octagon as usual. the shape and the positioning of san vitale’s porch, represent both a functional and symbolic solution. it acts like a monumental access to the church and like a filter between the external (earthly world) and internal (divine world), indicating also a clear psychological function to the visitor on arrival https://www.geometriefluide.com