San Tirso, a Mudejar masterpiece on the Camino de Santiago, is a 12th-century church in Sahagún. San Tirso was the model for the churches of Sahagún, including San Lorenzo, its typological twin, and Zamora, Valladolid, Ávila and Segovia. since 1931. Following the model of the Mudejar Theme Park in Olmedo.

Spain submitted in 2015 to UNESCO a "Retrospective Inventory - Associated Components" to extend the Camino to "Caminos de Santiago de Compostela: Caminos francés y Caminos del Norte de España". The church of San Tirso dates from 1423.

Between 1180 and 1190 the Mudejar church of San Tirso was built, opposite the former Royal Monastery of San Benito. The construction of the parish church must have begun in the first part of the century, as documented.

The liturgy of the church differs. Oriented towards the Qibla.

Its Romanesque-Mudejar floor plan has three naves and semicircular apses. Four elongated brick buttresses support the nave.

Well-carved limestone ashlars are grouped together in courses of up to 3 metres. The rest is brick.

Three apses. The nave of the epistle and the central apse are original. The central apse is of stone with good ashlars up to three metres, while the upper courses are of brick. The base and the wall of the main chapel are made of stone. Masonry tops the apses, adding contrast and a different architectural material.

The choir is clad in brick. In the lower half of the central apse, the blind semicircular arches are bent and supported alternately by modillions and attached circular columns whose shafts are built directly from the ashlar and then made of stone; at the top, they are inscribed in squares. The bent arches finish off and the squares finish off the lateral apses. Brick gondola mouldings adorn the roofs of the apses.

Instead of the transept, the impressive rectangular brick tower rises above the straight part of the central apse. This peculiar position defines the Mudejar architecture of Sahagún. The former dome of the Monastery of San Benito may have inspired the design and truncated pyramid-shaped layout of the tower. The tower has a large body to support the upper structure and another hollow body. The hollow volume of the prismatic tower contains three storeys.

The naves are now separated by two white round arches, instead of the five moulded brick arches of the renovated interior of San Tirso. Two ancient arches divide the base of the church.

San Tirso today houses sacred art. Thus, the chapels and naves contain archaeological, religious and historical objects.