The Spanish California: why Cartagena exists thanks to a hill near La Unión

Cartagena is one of the finest port cities in Spain, and almost everyone who visits assumes the harbour is the reason the city sits where it does. That is only half true. Cartagena was founded for what lay in the hills behind it — ore, silver-bearing ore, in quantities capable of financing a war economy. Without that hill there would have been no city, and certainly not in this spot.

That story runs right through to today, and not only in the pleasant direction. The same mining that made this coast rich also left behind one of the largest environmental files in Spain. Anyone house-hunting here drives straight through it: along the N-332, past orange-red hills full of chimneys, and past a bay that is no longer a bay.

Forty thousand men, twenty centuries ago

In the third century BC the Carthaginians founded Qart Hadasht here, later Carthago Nova and now Cartagena. Not for the view: the natural harbour lay within walking distance of ore seams containing silver.

We know the scale of it from a classical source. The geographer Strabo passes on what Polybius wrote about the silver mines near Carthago Nova: they lay some twenty stadia from the city, forty thousand workers were employed there, and in his day they brought the Roman people twenty-five thousand drachmas a day. That is not a sideline. That is the engine under an empire.

Forty thousand people below ground, to make a city above ground possible.

The conditions matched the scale. Diodorus describes miners who spent day and night in the galleries and left their health, and often their lives, there. The great majority of that work was done by slaves. That belongs to this heritage too, and it is not a detail you will find in a tourist brochure.

Cabezo Rajao: the hill with the gash

The best-known site of that early mining sits on the boundary between Cartagena and La Unión: Cabezo Rajao. The name means something like split hill, and it is well earned. At the surface here ran a seam of galena argentífera — lead sulphide with silver in it — which was hacked out with picks. What remained was a large gash straight through the summit.

Important for getting the picture right: this was not about seams of pure silver. The silver sat inside the lead. It made the region famous, but in tonnage terms this was always lead, and later zinc and iron as well.

What you see on the hill today is a layered monument. The Roman cut, and on top of it the nineteenth- and twentieth-century layer: chimneys, engine houses, offices, washing plants and headframes belonging to the mines that worked here later. The complex is protected as a Bien de Interés Cultural in the Sitio Histórico category, and that protection extends across the whole site including the neighbouring Cabezo Agudo.

1840: the Spanish California

After the Roman period mining largely fell silent. Only around 1840 did the second fever begin, and it was fiercer than the first. Within a few years more than fifteen hundred mining concessions were applied for in the Sierra Minera. The region earned the nickname this article’s headline refers back to: the Spanish California.

The figures are considerable: between 1860 and 1900 roughly 24 per cent of total Spanish lead production came from this area, making it one of the most important producers in the world. In 1860 La Unión separated from Cartagena and became an independent municipality. At its peak some 36,000 people lived there — well over double today’s figure.

Those people came from far away, above all from Almería and the rest of Andalusia. They brought their music with them, and below ground it changed character. That is how the flamenco styles of the Levante came about: the mineras and cartageneras, literally miners’ songs. La Unión owes its second life to them — the annual Cante de las Minas festival is an international name and pulls the region out of the shadows every autumn.

Portmán: the bay that disappeared

And now the other side of the story. In antiquity Portmán was a real harbour — the Roman name Portus Magnus says enough. Well into the twentieth century there was a natural bay here with a village beside it.

How important that harbour was is clear from what lay in the ground at the edge of the bay. At the Villa Romana Huerto del Paturro, discovered in 1969, some twelve rooms have now been documented, spread across terraces linked to one another and to the sea by stairs. Mosaics, imported marble and wall paintings came to light, along with a bath complex. The villa also had a productive side: salted fish, garum and esparto, shipped out by sea. At the end of the third century it was abandoned for good.

From the 1950s onwards mining changed character. Underground galleries gave way to large-scale opencast working, with washing plants producing enormous quantities of fine waste material. That waste did not go to a settling pond. It went into the sea. Between 1957 and 1990 roughly sixty million tonnes of mineral waste were discharged into the bay. The bay filled up, the coastline advanced hundreds of metres, and what remains is the orange-red plain that lies there now.

The largest company in the area was Peñarroya, which at its peak in 1987 accounted for roughly forty per cent of Spanish lead production and ten per cent of zinc production. In 1991 the mines closed for good, through exhaustion of the workable reserves and falling metal prices. What was left behind was a region without work and with a landscape waiting to be cleaned up.

Where the file stands now

Restoring the bay has been under way for decades, and it is still not settled. This is not closed history but a live file — and that is exactly why it matters to buyers.

In February 2026 the Ministry for Ecological Transition lifted the temporary suspension of the design contract. Since then the design firm may continue work on the implementation project and the environmental impact assessment, without being strictly tied to one previously presented option, but incorporating the conclusions of the CEDEX studies. Once both documents are ready, a public consultation round follows and advice is sought from other authorities and scientific bodies.

We take no side in this debate. What we do note: no final decision has been taken, and as long as that is the case, the future of the bay and the village behind it remains uncertain.

What this means if you want to buy here

Now the part a selling party rarely raises unprompted. Compare asking prices in La Unión, Portmán and the villages of the Sierra Minera with those on the Mar Menor or at Cabo de Palos and you see a substantial gap. That gap has reasons, and those reasons are knowable.

• Soil quality. More than a century of ore processing leaves traces. Parts of the area contain old settling ponds, spoil heaps and processing sites. That does not mean every plot is a problem — it means you need to know exactly where the plot lies and what the municipal and regional maps say about it.
• Ramblas and run-off. In heavy rain water runs down dry beds that cut straight through old mining ground. That combines flood risk with material being carried along.
• Planning uncertainty. As long as the restoration project for the bay is not final, the future of the immediate surroundings is not fixed either. Going ahead means years of works; delay means the current situation stays.
• Protected status. Around a Sitio Histórico such as Cabezo Rajao there are restrictions on what is permitted on and around the site. That is good news for the heritage, but anyone with plans for a nearby plot needs to know those restrictions in advance.
• Amenities and lettability. This is not a tourist resort. For permanent living that can be a plus; for rental yield it is a very different story from the Mar Menor.

None of this is a reason to write the area off. There are people who live here very deliberately: close to Cartagena, close to Cabo de Palos, with space and a landscape that resembles nowhere else. It is a reason to look address by address rather than town by town, and to ask those questions before the offer rather than after it.

We make no predictions about price development. What we do see: in areas with a live government file, the difference between a good and a bad purchase comes down mainly to knowing in advance what is at play.

Seeing it for yourself

This is an area best seen with a guide. Isolated ruins say little; the story around them is what makes it comprehensible. Part of the terrain is also unsafe or closed off — do not go exploring old shafts or spoil heaps on your own.

Mediterranean Cartagena Tours runs guided walks through this heritage. At the time of writing three dates are planned:

From the Costa Cálida and the southern Costa Blanca this makes a good morning out: from San Pedro del Pinatar and Los Alcázares it is a thirty to forty-five minute drive, and Cartagena itself sits right next door for the afternoon.

And while you are there

Immediately east of Portmán begins the Calblanque regional park, which according to the signage on site falls within the same Sierra Minera de Cartagena-La Unión. There, at the Barranco del Moro, runs a paved road whose origins go back to Roman times, later brought back into use by nineteenth-century mining. On Monte de las Cenizas there is also a coastal battery, with a gateway you would not expect in this landscape.

The area at a glance: Cartagena on the left, La Unión in the middle, Portmán on the coast. Map data © OpenStreetMap contributors.

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