The church of San Martín de Tours is an outstanding Catholic temple of the Romanesque style, built in the second half of the 11th century. Located along the Camino de Santiago, this church is recognized as one of the most representative examples of European Romanesque architecture.

In 2015, the church of San Martín was included in the documentation submitted by Spain to Unesco and the European Union during the extension of the recognition of the Camino de Santiago to "Caminos de Santiago de Compostela: Camino francés y Caminos del Norte de España". In this documentation, called "Retrospective Inventory - Associated Elements", the church appears at number 1326.

Built by order of Doña Mayor de Castilla as part of a monastery that no longer exists, the church of San Martín de Tours de Frómista dates from the second half of the 11th century. The first mentions of this church appear in documents from 1066, when it was already in the process of construction. Its architectural style is influenced by the Romanesque style of Palencia and the cathedral of Jaca, suggesting that some of the stonemasons who worked in Jaca also participated in this construction.

In 1118, the church became part of the Cluniac priory of San Zoilo, in Carrión de los Condes. Throughout the 13th century, the monks leased it to cover their economic needs, ceding it to Don Juan Gómez de Manzanedo, and it was leased on multiple subsequent occasions. During the 15th century, the temple underwent several modifications, such as the construction of a bell tower over the original dome and some rooms used as sacristy. Due to progressive deterioration, at the end of the 19th century, the church was declared unfit for worship. The deterioration accelerated after its closure, with detachments in the vault and walls.

In 1894, the church was declared a National Monument, which allowed a restoration process to begin. The architect Manuel Aníbal Álvarez Amoroso led the restoration work, with the objective of returning the church to its original appearance. This involved the elimination of elements added in later centuries. The most damaged capitals and corbels were transferred to the Archaeological Museum of Palencia and replaced by reproductions. The restoration was completed in 1904 and the church was reopened to the public. Inside the church a model is exhibited showing its state prior to the restoration. In 2010, maintenance and restoration work was carried out on the stained glass windows.

The church of San Martín de Frómista presents an aspect characteristic of the Romanesque style of its time. Its structure is marked by an octagonal dome over the transept and two cylindrical towers located at the ends of the main facade. The three naves of the temple, covered with barrel vault, end in semicircular apses, the central nave being wider and higher than the lateral ones.

The exterior walls are made of stone and have windows with semicircular arches in the apses and on the sides. The decoration includes a checkered stone cornice at different heights and more than 300 carved corbels under the eaves of the doors and roofs, with figures of animals, humans and mythological creatures. The church has four entrances: one to the north, one to the west and two to the south, one of them being the main entrance to the temple.

The western towers are crowned with a rooster, although the one in the south tower has been lost due to a lightning strike. The western and transept gables are topped with a circular ornament containing a kicked cross in bas-relief. Also visible are exterior buttresses that reinforce the structure.

The interior of San Martín de Tours has a basilica plan with three naves of different sizes separated by composite pillars. The central nave is wider than the lateral ones, and all three end in semicircular apses. The basilica plan is combined with a Latin cross form, with the octagonal dome over the transept. In this case, the transition from the square to the round structure is made by means of trumpets, instead of pendentives, as would be common in the later Gothic style.

Since the central nave lacks a clerestory and its vaults begin at the same height as the collateral ones, the space before the transept has the structure of a pseudo-basilica. In the apses several medieval sculptures are preserved, highlighting a Christ of the thirteenth century located in the apse of the central nave.

The interior of the temple, although sober in general, presents interesting decorative elements. The capitals of the columns, some of them modern replicas, are adorned with vegetal, animal and narrative motifs. Among the most outstanding are the capitals representing the story of Adam and Eve, the fable of "The Fox and the Raven", the goddess Cybele, and the so-called "capital of the Orestiad". On the access door to the north tower, a tympanum decorated with a six-armed chrism is reminiscent of those present in San Zoilo de Carrión de los Condes and in the Basilica of San Isidoro de León.

In addition, the checkerboard motif seen on the exterior cornices is also found on the interior of the temple, arranged at different heights, adding coherence to the decorative design of the building.