The church of San Juan Bautista is a small temple, archetypal of the rural Romanesque style in Palencia. It is located in the Huerta de Guadián Park in the city of Palencia. It was declared a Historic-Artistic Monument in 1981, which means that it currently has the category of Asset of Cultural Interest.

It was the parish church of the town of Villanueva del Río, near Aguilar de Campoo. It is already mentioned in documents from the 11th and 12th centuries, although in its current configuration it appears as a building constructed around the second half of the 12th century, with some transitional elements, such as the use of pointed arches.

The entire village and the church were affected by the design and subsequent construction of the Aguilar reservoir in the 1960s, which completely flooded the land on which they stood. To prevent the loss of the monument, already considered one of the greatest exponents of rural Romanesque architecture in the north, it was dismantled stone by stone in its original location and all its architectural elements were stored. Several possible uses and locations for the building were considered, such as serving as a new hermitage for the patron saint of Aguilar, the Virgen del Llano, whose hermitage had also been rendered inaccessible by the construction of the reservoir.

In the end, this and other options were discarded and it was decided to move it to one of the busiest public parks in the city of Palencia, the Huerta de Guadián. Part of the numbering of the ashlars used by the conservators for the reconstruction can still be seen at the head of the church. In the transfer, some elements were altered or lost, the most notable of these being the tower-spire that enclosed the building towards the foot, although at least in part it was later than the Romanesque construction. The building remained under construction from 1972 until 1980. In that year, the Directorate General of Architecture granted a subsidy of seven million pesetas, which allowed the reconstruction to be successfully completed.

It is a small church, as befits a small rural village in the Montaña Palentina. The fact that the building has not undergone any alterations or modifications over the centuries can be considered exceptional, which explains its stylistic homogeneity. The ground plan has a single rectangular nave with a chevet that ends in a semicircular apse.

On the outside, the apse drum is reinforced by two buttresses that reach half the height of the wall. Two lines of fascia run along the chancel, the lower one with decorative grouting, while the upper one has plain mouldings. In the centre of the apse, there is a small loophole-shaped window decorated with two columns with historiated capitals. The doorway occupies, both in width and height, most of the southern wall.

The section in which it opens, which is very prominent, is surmounted by a canopy on corbels. It consists of six archivolts of flared arches that start from a continuous abacus, supported by three columns that alternate with three semi-columns, all of which have capitals with vegetal motifs. The archivolts are made up of mouldings, mouldings, and mouldings decorated with combinations of motifs, among which are repeated balls and diamond-shaped points. The eaves of the building are supported by a series of corbels, all of which are plain except for those in the apse, which have very diverse geometric or figurative decorations.

The interior is notable for the variety of decorative elements from the Romanesque repertoire. The nave is covered with a pointed barrel vault, reinforced by pointed transverse arches. The supports alternate square pilasters with embedded semi-columns, which end in historiated capitals with varied decoration. The apse is covered with a quarter-sphere vault.

Striking double blind arcades decorate the straight section of the chancel that precedes the apse. The southern arches are semicircular, while the northern ones have very pointed tri-lobed arches. The capitals on which they rest show fantastic decoration of interlacing or waves alternating with human figures, scrolls with fleshy vegetal decoration and harpies. The decoration is completed by a crest of quatrefoil flowers and vegetal motifs.

Nowadays, the temple has been deconsecrated and houses an interpretation centre of the Romanesque style in Palencia, which is open to the public during the summer months and holidays.