Founded by the Phoenicians as Gadir around 1100BC, Cadiz is thought to be the oldest town in Spain. The name Gadir means "walled town", so the site has been fortified for over 3000 years. Cadiz is in an ideal location for defence. The town stands on a peninsular that has a narrow isthmus linking it to the mainland. Between the isthmus and the mainland itself is an expanse of marshy ground known as the Isla de Leon. The bay of Cadiz, next to the town, provided a safe haven for shipping. In medieval times the town was surrounded by walls, which were sufficient to repell the raids of the Barbary Corsairs during the 16th century.
However, Cadiz was to face a more determined enemy in the form of the English. The first English attack on Cadiz occurred in 1587, when Sir Francis Drake sailed into the harbour and destroyed the shipping there, delaying the Spanish Armada for a year. This event became known as "singeing the King of Spain's beard". Another English attack in 1596 was far more devastating. The English troops landed just north of the town and captured it by assault. At the time of the 1596 attack Cadiz had relatively few artillery fortifications. A small fort called San Felipe on the north side of the town guarded the harbour entrance and after the 1587 attack a small battery had ben built at Puntales to protect the inner harbour, but the town itself had only medieval walls.
The attack of 1596 left the city of Cadiz in ruins. The authorities even considered abandoning the town altogether, but eventually they decided to rebuild it and construct new defences. The new fortifications were designed by the engineer Cristóbal de Rojas. De Rojas had in fact made recommendations that the fortifications of Cadiz be strengthened several years before the 1596 attack but only in its aftermath were his suggestions taken on board. He built a line of modern angular artillery fortifications that extended around the end of the peninsular. This perimeter was longer than was necessary to surround the town itself, but it meant that the entire coastline to north was defended. This denied an attacker the possibility of landing next to the town (as the English had done in 1596) and forced them to attack along the isthmus instead.
Arguably the most important important part of de Rojas' fortifications were the two half-bastions that flanked the Puerta de Tierra (land gate). These bastions (San Roque and Santa Elena) guarded the only land approach to Cadiz and this front was the most likely to place an attack. The gate itself stood in the curtain wall between the two bastions.
The two half-bastions were arrow-headed bastions with squared "orillons". This feature is typical of the Italian school of fortification and it shows the Italian influence on de Rojas' designs. Italian engineers favoured recessed flanks because of the additional protection they provided for the guns behind the orillon. Although the fortifications of Cadiz were significantly reinforced over the centuries, this feature of the land front has remained unchanged.
Running north and west from the land front, on both sides of the peninsular, de Rojas constructed walls that followed the coastline. On the north side, overlooking the quays, there were bastions and rectangular works on the walls but on the south side, facing the open sea, the trace was more irregular. These walls were built to guard against a surprise attack along the beach to bypass the land front, so they would never face artillery.
At the tip of the peninsular there is a beach known as la Caleta (the cove). This beach was considered particularly important for the defence of Cadiz. If an enemy managed to land troops at la Caleta, they would have been able to attack the town from behind, which was exactly what happened in 1596. There were two main elements to de Rojas' fortifications protecting la Caleta; the Baluarte del Orejón at the south end of the beach and the Castillo de Santa Catalina to the north. The Baluarte del Orejón was a small bastion that flanked the wall along the beach and also the Puerta de la Caleta, a small gate that gave access to the beach and the rocks, where the locals used to fish.
At the north end of la Caleta de Rojas built a small fort (Castillo de Santa Catalina). This fort had two half-bastions facing inland and star-shaped walls on the seaward side. Its guns covered the approach to la Caleta and deterred any enemy from attempting a landing. It is interesting to note that de Rojas did not attempt to rebuild the self-contained fort called San Felipe, which stood on the north side of the town and had been destroyed by the English attack. It is probable that he considered la Caleta to be the most vulnerable part of the defences and so he wanted to ensure it was given the best protection, hence the self-contained Castillo de Santa Catalina in this location. The Castillo San Felipe was evidently not worth rebuilding and it does not seem to have performed well in 1596. In any case the strategic value of the north side of the town was in the guns covering the harbour entrance, which is something de Rojas was able to exploit without rebuilding the old fort.
By the 1620s the new fortifications were mostly complete and Cadiz had been transformed into a strong fortress with powerful coastal defences and a strong land front. Although the city faced attacks by the English in 1625, 1655, 1702 and 1797, it was never captured and the fortifications proved their worth in each attack. In the 17th and 18th centuries work on the fortifications was mostly limited to minor improvements. In the 1670s, as Spain was being drawn into conflict with France and England, the seaward fortifications were strengthened. At this time the defences of la Caleta were modified slightly and the Baluarte de la Candelaria and Baluarte de la Soledad were constructed on the north side of the town.
The next major work was the construction of the Castillo de San Sebastián, which was built on a small rocky islet a few hundred metres from the western tip of the peninsular. This rocky islet close to the walls was too dangerous to leave undefended and it made a good platform for a coastal battery. An artillery tower had been built there in the early 17th century, but in the 1700s it was decided to build a larger fort.
The islet was in two sections; the smaller inner islet was closer to the town and the larger outer islet (where the original artillery tower was located) pointed out to sea. The new fort was built on the smaller inner islet, separated from the outer islet by a ditch that flooded at high tide. The fort was an irregular shape, following the edge of the islet, with a point facing towards the outer islet. Inside the walls were barracks and storehouses for its garrison. There are embrasures for guns on every side of the fort, but the parapets were thickest on the walls facing away from the town. The parapets facing the town are very thin, presumably to prevent them from being used against the town if the fort fell into the hands of an enemy.
The outer islet was partially surrounded by a loopholed wall and the existing artillery tower was left in place, but clearly the intention was to retreat into the new fort if a serious attack was mounted on the area. In the mid-19th century a large fort was built on the outer islet, supplementing the defences of the old fort and mounting newer longer range coastal artillery. Around the same time a causeway was built to link the fort to the town, so that it could be accessed even at high tide.
One of the last major modifications to the fortifications of the town itself came in the 1780s, when the massive Baluarte San Carlos was built. This half-bastion, which replaced an earlier smaller bastion, overlooks the port and protected the entrance to the harbour. The Baluarte San Carlos has an impressive 55 casemates (bomb-proof arches) and could mount 90 guns. A mole extending from the point of the bastion also had a gun battery on it.
Another important aspect of the fortifications of Cadiz is the large number of outlying forts constructed for the defence of the wider area. These were mostly coastal forts and batteries designed to protect Spanish shipping from naval attacks. The inner part of the Bay of Cadiz was entered through a narrow stretch of water between the isthmus on which Cadiz itself was built and the mainland. There were coastal batteries on either side of this entrance. The Castillo de San Lorenzo on the isthmus side was a simple battery in the 16th century, but was made into a square fort with two bastions facing the land by de Rojas in the 1600s. It was modified in the 18th century to have a wide curved battery facing the water. On the opposite side of the entrance were Fuerte de Matagorda, a small fort with two half-bastions facing the land, and the Castillo de San Luis, a battery dating from the 1600s that was rebuilt in the 1700s. Along the coast to the south was the island fort of Castillo de Sancti Petri, which guarded the seaward side of the Isla de Leon. There were also numerous smaller batteries lining the coast opposite Cadiz near the town of Santa Maria.
The Fuerte de la Cortadura (the "cut fort") was an outlying work on the narrowest part of the isthmus linking Cadiz to the mainland. It consisted of a front of two half-bastions that guarded the isthmus and prevented any enemy from approaching Cadiz. Further out was the Puente de Zuazo, a fortified bridge linking the Isla de Leon with the mainland. This bridge had a hornwork on the mainland end and a small redoubt on the Isla de Leon end.
The impressive array of fortifications that had developed around Cadiz over the 17th and 18th centuries were put to the test during the Napoleonic Wars. In February 1810 a French army arrived to lay siege to Cadiz. The Spanish defenders, along with their Allies the British and Portguese, managed to hold out for 2 and half years before the French were forced to retreat in August 1812, abandoning the siege. With their command of the sea, the Allies were able to keep supplying Cadiz so that the city did not run out of food. The Spanish blew up the Puente de Zuazo at the beginning of the siege and patrolled the Rio Sancti Petri, the channel between the Isla de Leon and the mainland, with gunboats. Dozens of extra batteries were built during the siege, denying the French any opportunity of forcing their way onto the island.
With the exception of the walls next to the port, most of the fortifications of Cadiz have survived intact to this day. The land front and the Puerta de Tierra are in good condition, with new arches through the walls either side of the old gate to let the traffic through - this is still the only land route into the old town. It is possible to walk along the top of the walls around the town, where a road/path runs. The walls on the south side of Cadiz have suffered by having large concrete blocks piled up against them. These blocks reduce the force of the waves on the old walls, but they also obscure most of the fortifications themselves! The sentry posts along these walls are also missing.
The fortifications around la Caleta are in a much better state. La Caleta itself is a popular beach, so the walls are easily accessible. The Castillo de Santa Catalina contains some exhibitions and displays on the history of the fort and it can be visited for free. The Castillo de San Sebastián cannot be visited at the moment, although there are plans to open the fort to the public at some stage. However it is possible to walk along the causeway to the fort and to walk around the outside at low tide.
The fortifications on the northern side of the town have been altered slightly and the original parapets have been replaced by balustrades. The Baluarte de la Candelaria is used for public performances and is not always open, but it is in good condition. The Baluarte de San Marcos is intact and freely accesible.
Many of the outlying forts have also survived, but they are not always in good condition. The Castillo de San Lorenzo is in excellent condition although it is occupied by the navy so the inside cannot be visited. The forts on the opposite side of the harbour, Matagorda and San Luis have been swept away by industrial developments, although the foundations of Matagorda have been exposed and can be visited. The Fuerte de la Cortadora exists although it is derelict. The best way to se it is from the road whilst driving into Cadiz. The fortifications of the Puente de Zuazo have partially survived and remnants of the other batteries along the Rio Sancti Petri can also be found. The impressive island fort of Castillo de Sancti Petri has been restored as part of the events surrounding the bicentenary of the Napoleonic siege of Cadiz. It can be visited on a boat trip.
Cadiz is an excellent fortress to visit, with well-preserved walls, some unconventional features and two self-contained forts. The Castillo de Santa Catalina is worth a visit in itself, especially as there is no entrance fee. There are also some good beaches right next to the town, which are very popular in the summer. Cadiz is well connected by road and the railway station is next to the Puerta de Tierra.
The following website has some interesting information on the Isla de Leon defences during the Napoleonic siege: Guardia Salinera Isleña