Gaztelugatxe

Where it sits. Gaztelugatxe is a tied islet on the open Biscay coast, about 35 kilometres northeast of Bilbao, administratively part of the municipality of Bermeo, with the village of Bakio three kilometres west. The rock rises to roughly 80 metres and is joined to the mainland by a stone causeway that crosses a natural arch in two long dog-legs before becoming a staircase up the seaward flank. The step count is usually given as 241, though no two people who climb them into a headwind ever agree. Just to the north lies Aketx, a second crag closed to visitors and colonised by European shags and yellow-legged gulls. The surrounding coast is folded Cretaceous rock, planed by the Atlantic into wave-cut platforms that surface at low tide, and the water under the bridge is deep, cold and rarely still.

A castle rock with no castle. The Basque name is literal: gaztelu means castle, aitz means crag. The islet was fortified long before it was holy, and its natural defences made it a refuge in the wars of the Lordship of Biscay. In 1334 the forces of Alfonso XI of Castile besieged the rebel lord Juan Nunez de Lara on this rock and failed to dislodge him. A chapel dedicated to John the Baptist is documented here from the tenth century, and local tradition ties the site to the Knights Templar, a claim repeated everywhere on the coast and supported by nothing in the archives. The hermitage has burned and been rebuilt more than once, most recently after a fire in 1978. What stands today is a modest single-nave chapel restored in the following decade, whitewashed inside, hung with votive offerings from local fishing families.

The ritual at the top. Reaching the chapel is the point of the climb, and the small ceremony attached to it is genuinely old rather than invented for visitors: ring the bell three times, make a wish, and — depending on which grandmother is consulted — stamp a foot on the flagstone by the door to turn away bad luck. On 24 June, the saint's day, and again on 31 July and 29 August, pilgrims come up in numbers and Mass is said in the chapel. Inside, the walls carry model boats and photographs left by seafarers. Outside, the terrace looks straight down eighty metres of cliff to water that shifts from green to near-black in a swell. The islet has been a protected biotope since 1998 and forms part of the Natura 2000 network.

On screen. In October 2016 the HBO production of Game of Thrones shot here for its seventh season, using the causeway and stairway as the approach to Dragonstone, the Targaryen island fortress. The hermitage at the summit was digitally erased and replaced with a gate and towers, but everything below the skyline — the arch, the dog-legs, the wet stone handrails — is real and unaltered.

• The season-seven opener, Dragonstone, shows Daenerys Targaryen's fleet standing in and her party walking the causeway up toward the gate.
• The Queen's Justice, the third episode, brings Jon Snow and Davos Seaworth ashore and up the same steps to their first meeting with her.

The shoot lasted only a few days. Its effect on visitor numbers was immediate and permanent.

Access is now controlled, and that matters. Before the series aired, Gaztelugatxe drew a few hundred thousand people a year. Afterwards the figure roughly doubled, the single-file causeway backed up badly, and the Biscay provincial council introduced a reservation system. Entry itself remains free, but through the busy season and on public holidays a timed ticket obtained in advance is compulsory, with a daily cap in the low thousands and slots that disappear weeks ahead for summer weekends. The site shuts entirely in high wind and heavy swell, and one weekday is generally held back for maintenance at peak times. Arriving on a July morning without a reservation is the most common way to waste a day on this coast.

What the climb demands. From the car park on the BI-3101 the walk down to the bridge takes 20 to 30 minutes on a paved track with a steady gradient, and the return climb — the hard part — comes at the end. Allow two hours for the round trip with the stairway included. The steps are uneven, sea-worn, frequently wet and entirely unshaded; this is no route for wheels, strollers or unreliable knees, and there is no water, no café and no shelter beyond the car park. Bizkaibus services running from Bilbao toward Bakio and Bermeo stop at the entrance. Late spring and early autumn combine workable light with manageable numbers, and the low western sun of late afternoon throws the arch into the relief that most photographs taken here are really chasing.