The Santa Iglesia Catedral de San Antolín is a temple of Catholic worship, the episcopal seat of the Diocese of Palencia, in the city of the same name.

It is dedicated to Saint Antolin the martyr, patron of Palencia, part of whose relics it conserves.

It is the third largest cathedral in Spain in terms of extension, and the second in terms of the length of the nave.

It is a construction of great proportions: 130 meters in length, with a width of 50 meters in the transept, plus as many in the cloister and chapter house; the apse is almost 42 meters high.

It is a predominantly Gothic building, although it retains previous elements, from the Visigoth and Romanesque times, and Renaissance, Baroque and Neoclassical decorative elements.

The construction began in the 14th century, being the only great Castilian cathedral started in that century.

The exterior lacks a proper main facade and is austere and massive, a situation that does not reflect the greatness of its interior, where more than twenty chapels of great artistic and historical interest and a multitude of works of art of all styles can be seen.

Although the construction of the Gothic cathedral lasted from the fourteenth to sixteenth centuries, in reality what is observed today has taken almost fourteen centuries to be built, since the oldest part of the Crypt of San Antolín dates from the seventh century and there were important works and reforms in the twentieth century.

The most recognizable element on the outside is the tower 55 m high, elevated and sober, somewhat rough considering its belonging to the Gothic style. Recent studies and excavations show that it was a military tower in the past and after fulfilling that function pinnacles and belfry were added as the only decoration. The floor plan of the cathedral is of a Latin cross and has the peculiarity of having a double transept, which is why it also has five doors, thus forming a plan in the shape of a patriarchal cross; This is due to the fact that halfway through construction it was decided to replace the original transept with a second, more monumental one. Both cruises are only marked in elevation and do not stand out in plan.

The cathedral is popularly called The Unknown Beauty. It was the first monument in the municipality of Palencia to be declared a National Monument, a distinction it obtained on November 3, 1929.