Santa Gadea del Cid

Santa Gadea del Cid holds a double layer of protection: the entire town was declared a Historic Site in April 1973, and the Monastery of El Espino received individual monument status in 1991.

The castle is in fact an ancient fortress, originally built by Pedro López de los Manrique and later reformed, that anchors the town's defensive identity. Alongside it stand the remains of a perimeter wall, a battlemented church tower, and two surviving gateways — with evidence suggesting a third once existed to the east. The walls served not only military purposes but also controlled access to the market, kept out smugglers and thieves, and enabled tax collection. These gates were a compulsory passage for travellers on the road to Bilbao.

The Puerta de la Villa is a pointed arch 2.55 metres wide, topped by a worn shield of the Padilla and Manrique families, flanked by arrow slits, and finished with two small Gothic arched openings. It once served as a jail. The Puerta de Abajo, or Puerta de las Eras, is heavier and more solid, built in rougher masonry that deteriorates in quality toward the top. A flat-carved human figure appears above it, and the inner side has a lintel ceiling with a pitched roof.

The Church of San Pedro traces its first documentary mention to 1012. Gothic in structure, built mainly in dressed stone, it has a conopial-arched main entrance and a second doorway with an unfinished Renaissance porch added later. The floor plan runs over 40 metres in length across three naves, two Gothic and one Renaissance, with Gothic vaulting, Romanesque grotesque capitals, and a major altarpiece in Plateresque style first discussed in 1492 but apparently not completed until 1539. A chapel beneath the bell tower has functioned as a parish museum since 1932.

The Hermitage of Nuestra Señora de las Eras, built in pure Romanesque style at the end of the period when Santa Gadea passed definitively into Castile under Alfonso VIII, sits on a hilltop facing the town. Its walls are 1.5 metres thick. The interior paintings are modern, imitating ashlar, stars, and interlacing patterns. A brotherhood called the Virgen de las Eras has been associated with it since antiquity.

The Hermitage of Nuestra Señora del Patrocinio has a semicircular arched doorway and a Baroque bell gable, built to commemorate apparitions of the Virgin of El Espino and later restored with direct participation from local residents.

The former Hospital of San Lázaro was founded in 1465 by Fernando Ortiz to shelter sick poor people and passing travellers. Carefully restored in 2010 using original materials and structure, it now operates as a rural guesthouse.

The Church Square is considered a fine example of traditional Castilian vernacular architecture. It was historically the site of the town market and today hosts the annual Medieval Supper, organised by the cultural association Las Candelas. Two of the town's original four stone crosses survive — one called Encima de la Villa, the other del Hoyo — both restored in 2004 and formerly visited during rogation processions.