Although the Roman settlement of Obulco was still important during the Visigothic era, it seems to have undergone significant decline. The town that the Muslims encountered was smaller than the Roman settlement and required defences that were better suited to its reduced size. Thus, Hisn Bulkuna, as they named it, was given a new wall and the highest point of the town, housing the majority of its civic, residential and religious buildings, was strengthened, to which end some of the old defences were repurposed. Recent archaeological excavations have provided the first hypothesis of the outline of the town’s Muslim wall, beyond which there were also extensive arrabals. The walled enclosure was crowned by 17 towers, of which eight are still standing. The population reached its height around the 12th and 13th centuries, while the town’s defences remained in place until they disappeared between the 17th and 18th centuries.

After the Castilians gained control of Porcuna, probably around 1240, the Order of Calatrava proceeded to strengthen the town’s defensive capabilities, which involved organising the settlement into three distinct areas. There was the alcázar, which served as a fortress and residence of the commander; the town centre, which stood on the site formerly occupied by the Islamic alcazaba, or citadel; and the walled residential areas adjoining the town centre, whose fortifications were known as the “lower walls”. We also know, from descriptions in the documentary sources, that a palace complex was built between the 14th and 15th centuries. In turn, the upper enclosure or alcázar had eight towers, of which the remains of five – some dating back to the Muslim era – have survived. There would also have been a keep, which has since disappeared and may have stood in the centre of the alcázar, and the imposing New Tower.

The interior of the enclosure was divided into two sections: a military area to the north, which housed the keep and its service areas (bread ovens, a kitchen, stables etc.); and a more palatial area to the south, which housed a number of important buildings including the Church of Santa Catalina, the armoury, and various residential and administrative spaces used by the Master of the Order. 

Three of the town’s gateways have been identified: the old Puerta de la Villa, of which the Arco de los Remedios, an arch standing next to the Town Hall, may have formed part; the Puerta de Martos, which is near the New Tower; and the Puerta Meridional, which now forms part of a residential building on Calle Aguilera. A detached tower has also been identified, which stood in front of the wall and was connected to it by a central passageway covered by half-barrel vaulting at the front and lowered vaulting at the back. 

The south end of the alcázar was protected by the New Tower, popularly known as Boabdil’s Tower as according to the sources, Boabdil was imprisoned there after being captured at the Battle of Lucena. This Gothic-Mudéjar tower has an octagonal layout, adjoins the alcázar walls and stands at a height of 28 metres. Its entrance is defended by a machiolation at the top of the structure, and just like the tower’s inner doors it is framed by a pointed arch. The windows on the first floor are set within multi-lobed double arches, which can also be found on other fortifications within the Order’s feudal estate in the Upper Guadalquivir region. The parapets on the tower’s terrace are raised on corbels, giving the appearance of a continuous machiolation. On the south façade there is a panel bearing the cross of the Order of Calatrava flanked on both sides by the coat of arms of the Guzmán family. We can also make out the following inscription: THE CONSTRUCTION OF THIS TOWER WAS ORDERED BY THE MOST VALIANT AND NOBLE KNIGHT LUIS DE GUZMAN, BY DIVINE PROVIDENCE THE MASTER OF CALATRAVA, IN THE YEAR OF OUR LORD ONE THOUSAND AND CCCXXXV. 

Internally, the tower has a solid ground floor, above which are two upper floors and a terrace, all of which are linked by stairs built into the north wall of the structure. The rooms are covered by rib-vaulted ceilings supported by corbels decorated with plant motifs, with keystones incorporating the heraldic emblem of the Order. Today, the tower houses the Porcuna Museum of Archaeology.

In the 17th century, the loss of its military function led to the gradual deterioration of the alcázar; a process that culminated with the Lisbon earthquake of 1755, which had a major impact on this area and caused extensive damage and destruction to the walls and towers. The bombardments inflicted during the Spanish Civil War also caused a great deal of damage to the remaining fortifications. Changes in the layout of the town ultimately concealed the defensive enclosures from view, and while some parts of the walls and towers survived by being put to use as dividing walls for residential buildings, sadly others were demolished. Additionally, since the middle of the 20th century the New Tower has undergone a number of aggressive interventions, which have altered its original appearance.

Cerro del Castillo is one of a series of flat-topped hills, and the town of Porcuna is spread out across several of these. The earliest occupation of Porcuna occurred between the Neolithic and Chalcolithic eras, in the 3rd millennium BC, when a community was established on the hills of Cerro de los Alcores and Cerro Albalate. This settlement survived into the Bronze Age and on into the Iberian period, when it became a polis known as Ipolca. Around the 7th century BC the settlement was transferred onto Cerro del Castillo, which is taller than the others.

Archaeological excavations appear to indicate that during the time of the Roman Republic, a substantial wall was built around the settlement (which at that time was known as Obulco). This wall survived until the end of the High Roman Empire, when some parts of the town began to be abandoned. Although the town remained important within the local area, it appears to have undergone significant decline during the Visigothic period. 

In 1232, Muhammad ibn Yusuf ibn Nasr ibn al-Ahmar (popularly known as Alhamar, and also as Muhammad I), who was born in Arjona, proclaimed himself sultan in Jaén and one year later extended his rule to encompass Porcuna and Córdoba. In 1234, he declared fealty to Ibn Hud (who had been appointed governor of Andalusia by the Abbasid caliph) in exchange for Ibn Hud’s recognition of his status as king of Jaén, Arjona and Porcuna. Between 1240 and March 1241, King Ferdinand III managed to capture this area and immediately granted it to the Order of Calatrava. The Order then made it one of the main commanderies in the feudal estate it had amassed in the Upper Guadalquivir region. 

The 13th and 14th centuries were marked by instability as a result of continuous Muslim incursions into the area. The Battle of Lucena in 1483 resulted in the defeat and capture of King Boabdil of Granada, who was imprisoned for a time in Porcuna. Consequently, the town’s New Tower became popularly known as “Boabdil’s Tower”.

At the end of the 17th century the Crown withdrew its funding for the maintenance of the Order of Calatrava’s fortifications, thereby kick-starting a process of abandonment and ruination. The Lisbon earthquake of 1755 had a major impact on Porcuna and caused serious damage to its defensive structures, which had already suffered significant deterioration.