Climb the stair inside the walls and work out that the castle and the church are one building, not two

Go into the crypt of Santa Quiteria at the entrance and listen to what it does to sound

Find the dome over the castle church, which Romanesque builders rarely attempted

Work out the sequence: fortress, then enlarged by Sancho Ramírez around 1071, then a house of canons under papal protection from 17 October 1071

Stand on the wall and look out over the Huesca plain — the reason it was built exactly here

Loarre was built in the 11th century on a rock spur above the Huesca plain and is considered the best-preserved Romanesque fortress in Europe — one of the finest surviving examples anywhere of Romanesque military and civil architecture together. Sancho Ramírez enlarged it around 1071 and founded a house of canons in it, and on 17 October that year Pope Alexander II took it under his protection. Peter I later moved the congregation to Montearagón and Loarre stopped being a monastery. It has a church with a dome, which is unusual in Romanesque, and a crypt with extraordinary acoustics.

Loarre: The Best-Preserved Romanesque Castle in Europe

Stand at the foot of the Pisón and look up 275 metres of overhanging conglomerate

Work out what the rock actually is: river cobbles and gravel cemented in the Miocene and stood on end by the Pyrenees

Find the Visera and work out where sixty metres of overhang puts the top relative to the bottom

Learn the names of the towers — el Puro, el Cuchillo, la Visera, el Tornillo — and where each name came from

Watch the griffon vultures at the Paredón de los Buitres, which is named for them

Climb here if you climb — and if you do not, walk the path round the base, which gets you underneath all of it

The Mallos are towers of Miocene conglomerate — cemented river cobbles and gravel — thrown up when the Pyrenees rose, and they reach 275 metres at the north spur of the Pisón. The walls are vertical or overhanging, which is why they are one of the great climbing grounds of Spain; the Visera is reckoned the biggest overhang in the country, sixty metres out from the base of the tower to the vertical of the top. Each mallo has its own name, some from houses in the village, some from their shape. They were made a natural monument in November 2016.

Mallos de Riglos: Vertical Conglomerate

Walk into the lower church and work out that the roof over your head is the mountain

Find the royal pantheon where kings of Aragon and Navarre were buried for five centuries

Go into the cloister under the overhang and look at the carved capitals

Find out what the founding legend of Aragon says happened here with Voto, Félix and Garci Ximénez

Find out what the monastery claimed to have kept, and where that object is said to be now

The old monastery of San Juan de la Peña is built directly under a vast rock overhang, with the cliff as its roof — the most important monastery in Aragon in the early Middle Ages, and the royal pantheon where kings of Aragon and Navarre were buried across five centuries. It reached its height under Sancho Ramírez. The founding legend of the kingdom of Aragon is set here: Christian fighters gathering with the hermits Voto and Félix and acclaiming Garci Ximénez as their leader. The Holy Grail was said to have been kept here before it went to Valencia.

San Juan de la Peña: A Monastery Under an Overhang

Walk the star-shaped ramparts of the Citadel of Jaca (Castle of San Pedro) — designed for Philip II in 1592 and never involved in a battle

Find the moat and drawbridge of the pentagonal fort, still the only way in

Inside Jaca Cathedral, find the carved capitals of the 11th-century Romanesque nave

Walk the arcaded main street connecting the cathedral to the citadel

Two buildings five minutes apart. The cathedral of San Pedro was begun in the last quarter of the 11th century on the initiative of Sancho Ramírez, at almost the same moment as Santiago de Compostela, and it carries the architectural vocabulary that then travelled the whole Camino — the chequerboard billet moulding and the ball ornament on the interior supports. The citadel is a five-pointed star fort on the Italian model, built outside the town walls and preserved essentially intact: ditch, bastions, scarps and counterscarps, barracks, powder stores and tunnels, entered across a three-arched bridge and a drawbridge. The Spanish army held it into modern times.

Jaca: Citadel and Cathedral

Walk the full 240m length of the station building and count some of its 365 windows

Find the section preserved as a small museum, documenting the station's role smuggling Nazi gold and hiding refugees between 1942–1944

Look for the plaque honouring Albert Le Lay, the French border guard called "the Schindler of Canfranc" for helping refugees escape

Walk a stretch of the disused rail line heading toward the sealed French border tunnel — the international route has been closed since 1970

Canfranc International station is 241 metres long with seventy-five doors on each side, built to the design of the engineer Fernando Ramírez de Dampierre and modelled on 19th-century French palace architecture. It took five years and was inaugurated on 18 July 1928. International services stopped between 1945 and 1949 over a falling-out with the French government, and then ended altogether on 27 March 1970 when a French freight train derailed and brought down the L'Estanguet bridge on the far side of the border. A new passenger station opened on 15 April 2021 in two rehabilitated freight sheds, and in 2023 a luxury hotel opened inside the old building itself.

Canfranc: The Belle Époque Station on the Border

Go to the costume museum in Ansó church and work out how many pieces the traditional dress has

Come on the last Sunday in August, when the village wears it

Find out what cheso is and how a dialect survives in one valley and not the next

Look at the chimneys on the houses and work out what they were built that size for

Drive up into the Selva de Oza and walk to the Boca del Infierno gorge

Ansó and Hecho are the two westernmost valleys of the Aragonese Pyrenees, and they kept a distinct identity long after the rest — their own dialect, Aragonese in a form called cheso in Hecho, and a traditional women's costume of such complexity that it is one of the most elaborate surviving folk dresses in Europe, still brought out for the last Sunday in August. The villages are stone and slate with enormous chimneys. Behind them the Selva de Oza and the Valles Occidentales park run up to the French border.

Ansó and the Western Valleys

Drive the eight kilometres up the dead-end valley and work out that the spa is in a cirque with no way on

Take the waters, which the Romans were already exploiting here

Work out what the 19th century did to this valley and how many people the spa supported

Walk up to the ibones above the resort, which are glacial lakes at altitude

Come in winter for the Panticosa-Los Lagos ski area on the other side of the valley

Eight kilometres up a dead-end valley from Panticosa, in a glacial cirque ringed by peaks, is a thermal spa built in the 19th century on a Roman-era exploitation of the same springs. The 19th century was its high point — the village itself is mostly buildings from that period, when Panticosa held nearly nine hundred people on the back of the spa. The waters come out of the mountain in a place where there is nothing else, and the ibones, the high glacial lakes above the resort, are a short and very steep walk further up.

Panticosa: A Roman Spa in a Glacial Cirque

Walk the wall up the ridge above the town and look back down into it

Work out the political anomaly: an Islamic taifa handed to a Christian family by agreement, then held independent of Castile and Aragon from 1170, with its own bishop

Find the rodeno — the reddish local stone that gives every building in the town the same colour

Go into the Cathedral of El Salvador in the middle of the old town

Look at the forged ironwork on the houses, which is the local vernacular and is everywhere once you notice it

Albarracín is named after the Banu Razin, a Berber clan who made themselves the sovereign dynasty of their own taifa here in the 11th century. What happened next is the unusual part: the taifa passed to the Azagra, a Christian family of Navarrese lineage, by cession rather than conquest, and from 1170 they held it independent of both Castile and Aragon — to the point of running their own bishopric. The town is built of rodeno, the local reddish stone, and is walled, vertical and almost entirely intact.