In 1880 and 1881, the church underwent a major expansion: the new altar end and transept were built, with an impressive dome over an octagonal base on squinches, which create an interplay of star-shaped ribs. 

The main facade is austere, and the side is divided into two bodies height-wise. Inside, the church has a single nave with a crosswise transept and five chapels on either side, while the roof has ribbed vaults. The church is presided over by a Gothic image of Mare de Déu de Sineu (Our Lady of Sineu), one of the so-called verges-sagrari (virgin-sanctuaries) wrought by Gabriel Mòger in 1509. 

The fourth chapel on the left is the Capella Fonda. It is surmounted by a centrally-placed dome and harbours an impressive altarpiece of Mare de Déu del Roser (Our Lady of the Rosary) dating from 1672, with paintings by Rafel Guitard.

The belfry was built in 1549, and it is separate from the church, although they are connected by an elevated covered walkway popularly known as “el pontet de Santa Bàrbara” (the little Saint Barbara bridge). Its square layout features seven stretches separated by moulding that end in a pyramid-shaped crown. 

In front of the rectory you can admire the monument to Saint Mark, a sculpture by Joan Maimó dating from 1945. The lion, this apostle’s symbol, appears winged and bearing the coat-of-arms of Sineu. King James II may well have shared his devotion to this saint with the peasants of Sineu, who prayed to Saint Mark, petitioning him for springtime rains. Over time, he became the patron saint of the town.