The Castillo de la Luz is the oldest fortress in the Canary Islands: a squat, thick-walled stone block beside the harbour of Las Palmas de Gran Canaria, begun in the years just after the Castilian conquest and rebuilt in stone in the sixteenth century to defend the anchorage from pirates. It now houses the Fundación de Arte y Pensamiento Martín Chirino, a museum devoted to the Las Palmas-born sculptor who became one of the most important Spanish artists of the twentieth century.

The combination is better than it sounds. A five-hundred-year-old fort with metre-thick walls and almost no windows turns out to be a very good place to show large iron sculpture: the rooms are dim, cool and heavy, and Chirino's black spirals of forged iron sit in them as though they had been made for the space. Which, in the case of several pieces, they had.

It stands in the Isleta district at the northern end of the city, beside the Parque de Santa Catalina and a short walk from the cruise terminal and Las Canteras beach. Most visitors to Las Palmas walk within three hundred metres of it and never notice it is there — it sits low, behind a dry moat, surrounded by a small park, looking more like a municipal water tank than a castle.

Why a fort here at all

The reason is the shape of the coast. La Isleta is a rocky peninsula joined to the rest of Gran Canaria by a low sandy isthmus, and the bay it shelters — the Puerto de la Luz — is the only naturally protected deep-water anchorage on this side of the island. Anyone holding that bay held the trade. Anyone taking it could sack the town.

After the conquest of Gran Canaria in 1483, the new Castilian administration needed to secure the landing place, and a first fortification went up on the beach here in the 1490s. It was wood and earth, and it did not last. The stone castle you see, a square keep with round bastions at the corners, dates in essence from the middle of the sixteenth century, when Spain's Atlantic shipping and the treasure route to the Americas made these islands a target worth attacking. The wider story of that period is in our account of the corsairs who raided the Canaries, and the fort is its most tangible survivor.

Drake, Van der Does and the raid that worked

Two attacks define the castle's history, and only one of them went the attacker's way.

In 1595 an English fleet under Francis Drake and John Hawkins — on the voyage that would kill both of them in the Caribbean — put in at Las Palmas to take on water and supplies. The shore batteries and the town's defenders drove them off. Drake gave up on the city and sailed west. For a place that spent the century braced for an English attack, it was a famous morning, and islanders still tell it with some satisfaction.

Four years later the Dutch came, and it went very differently. In 1599 Pieter van der Does arrived off Las Palmas with a large fleet — accounts put it at over seventy ships and many thousands of men — landed troops along the beach, and took the town. The castle fell. Van der Does held Las Palmas for several days, demanded a ransom that was not paid, and burned a good part of the city including the cathedral archives before withdrawing, harried by defenders who had fallen back into the hills. The loss of those records is one reason so much of the islands' early history is thin.

The fort you walk into today is not the fort Van der Does took. It was damaged in 1599, patched and altered repeatedly over the following centuries, used as a store and even a private house, and then heavily restored in the 1960s and again before the museum opened in 2015. What is genuinely sixteenth-century is the mass of the walls and the basic plan.

The beach that vanished

This is the detail that changes how you read the building. The Castillo de la Luz was built on the shoreline. Its guns covered a beach; the sea came up to the walls, and boats landed in front of it. Today it stands several hundred metres inland, ringed by a lawn, with warehouses and container cranes between it and the water.

The sea did not retreat. The city advanced. From the 1880s onwards the Puerto de la Luz was dug out, dredged and extended into one of the great bunkering ports of the Atlantic — coaling station first, then oil, then containers and cruise ships — and each phase of reclamation pushed the waterfront further out. The fort that had been the point where Gran Canaria met the ocean ended up stranded in a car park. If you want to understand what the modern port did to this city, stand at the castle wall and look for the sea you cannot see.

Martín Chirino, and why he is here

Martín Chirino (1925-2019) was born in Las Palmas, the son of a shipyard foreman, and grew up around the forges and metalworkers of this exact district. He became one of the founders of El Paso, the group that dragged Spanish art out of the grey conservatism of the 1950s, and spent six decades making sculpture out of forged iron — above all the espirales, curling black coils that uncoil out of a mass of metal like a wave or a wind.

The spiral came from home. Chirino traced it to the carved spiral motifs the pre-Hispanic Canarians left on rock and pottery, which you can see for yourself at the painted cave at Gáldar and in the Museo Canario's collection. He also spoke about Atlantic wind and the sea shaping the form. Whatever the origin, the result is a body of work that is unmistakably from these islands and completely at home in international modernism — the same trick the painter Néstor attempted a generation earlier at Pueblo Canario, pulled off in iron.

The foundation opened here in 2015, in the artist's lifetime, with his involvement. The collection takes in sculpture, drawings and archive material, and there is a temporary exhibition programme alongside it. Expect a relatively small display rather than a vast survey; the building sets the limits.

Inside the castle

The restoration by the architect Nieto Sobejano wrapped the old fort in a low new structure sunk into the ground around it, so that you enter through a modern concrete space and then step into the sixteenth-century interior. The moat was excavated and left open. The join between old and new is deliberately plain, which is a mercy.

Look for the change in the stonework as you go round the outside. The lower courses are dark local basalt, rough and irregular; higher up there is paler, better-dressed stone from later rebuilds. Five centuries of patching are legible in about thirty seconds if you know to look.

Inside, the rooms are simple: thick walls, vaulted ceilings, a spiral stair, a flat roof terrace you can usually walk out onto for a view across to La Isleta. There is a Gothic doorway of some age on one face. Allow forty-five minutes to an hour unless there is a temporary show you want to linger over.

Tickets, hours and practicalities

Entry is charged and is modest, with the usual reductions and at least one regular free-access slot; the foundation publishes current prices and opening days on its own site, and both have been revised since it opened, so check rather than assume. It closes at least one day a week, and it is not a place to turn up at ten past two without looking, because the midday break still governs a good deal of the city.

The interior has level access through the new entrance, though the upper level and the roof involve stairs — worth a call ahead if that matters, and the wider picture is in our guide to getting around the islands with limited mobility. There is no café inside; there are plenty around the Parque Santa Catalina, two minutes away.

Combine it with the Museo Elder, the hands-on science museum in the old port warehouse across the square, if you have children with you. The castle will hold a curious adult for an hour and a bored eight-year-old for about seven minutes; the Elder solves that problem within a two-minute walk.

Getting there

The castle is on Calle Juan Rejón in the Isleta, immediately behind the Parque de Santa Catalina. From Las Canteras beach it is a walk of five to ten minutes across the isthmus. From the cruise terminal it is close enough to do on foot, which makes it one of the more rewarding short stops for anyone in port for the day.

City buses run along the seafront from Vegueta and the old town in about twenty minutes, and the long-distance coaches from the southern resorts terminate at Santa Catalina station, almost outside the door. Street parking in the Isleta is metered and tight; the underground car parks around the park are the sane option.

The bottom line

The Castillo de la Luz is a small visit and an unusually good one. You get the oldest military building in the archipelago, the story of two of the most dramatic days in the city's history, and a serious collection by an artist who was born a few streets away — in under an hour, for the price of a couple of coffees.

It works best as part of a walk around the northern end of Las Palmas: the beach, the park, the castle, the Elder, and a late lunch of fish somewhere behind the promenade. Pair it with Vegueta at the other end of the city and you have the two ends of the same story, five hundred years apart, joined by a single bus route. If the idea of a fortress full of modern art appeals, the eighteenth-century Castillo de San José above Arrecife harbour does the same thing on Lanzarote, with César Manrique behind the conversion.