Elements pertinent to the ancient Catalan- Aragonese church plant are rare and difficult to detect (fig. 1).

Fig. 1 - Map of the archaeological area of S. Eulalia and its various stages with indication of structures indicating the primitive church: a. buttress supporting the elevation; b. west side of the porticus; c. side wall going east/west; d. wall structure built on two arches in an ancient structure probably outside the archaeological area (from Martorelli 2013, p. 254, fig. 5).

Amongst these there is an oblique wall still visible in the outer facade also identified under the church at the foundation level (fig. 2): it was probably a buttress which overlapped the rest of the portico, then already destroyed and covered by layers of earth.

Fig. 2 - Oblique wall and tangent structure with lower arches visible in the archaeological area (photo by Unicity S.p.A.).

Another structure then stood on this oblique one, facing East-West, forming the North side of a horseshoe-shaped structure (fig. 3), which still supports the facade just for the width of the central nave.

Fig. 3 - Facade of the church of S. Eulalia: a and b are the side walls of the horseshoe-shaped structure, what remains of the primitive church (from Martorelli 2013, p. 256, fig. 6).

It is possibly the oldest masonry structure (even though at foundation level), so what remains of the single hall church built in the XIV century. The constructions of the new Iberian rulers in Cagliari (the ancient basilica of Bonaria and San Giacomo) or in their homeland (St. Agata in Barcelona) suggest a single-nave church, small in size, with no side chapels, added in the 16th century.