Go into the church of Santiago, consecrated in 937, the only building left of Genadio's monastery

Walk the lanes of the village, its old stone houses kept round the church

Walk into the Valle del Silencio to the cave of Saint Genadio

Look for the Roman water channels in the valley

Peñalba de Santiago is a small stone village high in the Aquilianos mountains above Ponferrada, built round one of the jewels of Mozarabic architecture: the church of Santiago, begun on the initiative of Saint Genadio of Astorga and consecrated in 937 by his disciple Abbot Salomón. It is the only building left standing of a monastery that has vanished. These mountains were so full of hermits and monasteries from the 8th century on that they were called the Leonese Thebaid. Below the village the Valle del Silencio runs up to the foot of Pico Tuerto, 2,051 metres, past the cave of Saint Genadio and the remains of Roman water channels.

Peñalba de Santiago: A Mozarabic Church in the Valley of Silence

Go into the Templar castle above the Sil and work out why the order was given this particular town

Find out what pons ferrata means and which bridge of about 1082 it refers to

Taste Bierzo Mencía and work out why this basin grows something the rest of León does not

Walk a stretch of the Camino through the basin towards the climb at O Cebreiro

Around 1082 Bishop Osmundo of Astorga, with Alfonso VI of León, had a bridge built over the Sil so that pilgrims could stop fording it further upstream. The bridge was reinforced with iron — pons ferrata — and the town that grew around it took the name. The Templars were later given the place to protect the road. Their castle still dominates it. The Bierzo around it is a basin ringed by mountains that makes it climatically and culturally separate from the rest of León — it grows Mencía, it has its own appellation, and it feels much more like Galicia than like Castile. The Camino Francés runs straight through on its way to O Cebreiro.

Ponferrada and the Bierzo

Go to the Orellán viewpoint and look down over what is essentially an industrial landscape two thousand years old

Work out what ruina montium means: water driven into galleries at pressure until the mountain collapsed from inside

Walk into the Orellán or La Cuevona galleries and see the tunnels the water was forced through

Find Lake Carucedo and work out that it is made of mining spoil

Work out the scale of the hydraulics: over 400 kilometres of channels, built to demolish a mountain

Las Médulas is the largest open-cast gold mine of the entire Roman empire, and what is left of it is a landscape of red sand peaks and gorges now half covered in chestnut and oak. The Romans began working here under Augustus, who personally directed most of the campaigns in this region between 26 and 19 BC, because gold was needed for the new aureus coinage. The method was ruina montium: over 400 kilometres of channels brought water into galleries cut inside the mountain until the pressure burst it apart. The spoil created Lake Carucedo. It became a World Heritage Site and a protected cultural asset in 1996.

Las Médulas: The Mountain Rome Washed Away

Find the Puerta del Perdón on the church of Santiago and work out exactly what it was for

Work out how far a pilgrim has walked to reach it and what is still ahead of them

Walk the Calle del Agua, the street of the old noble houses, down to the river

Go into the castle-palace of the marquises at the top of the town

Look west at the climb to O Cebreiro, which is what the door was there to excuse

The church of Santiago at Villafranca del Bierzo has a Puerta del Perdón, and it exists for a specific and humane reason: a pilgrim who had walked this far and was too ill to cross the mountains into Galicia could pass through this door and receive the same indulgence as if they had reached Compostela. It is one of very few such doors anywhere on the route. The town sits where the Burbia and Valcarce meet at the western edge of the Bierzo, with the Ancares behind it, and it has the look of a Galician town that has not quite arrived.

Villafranca del Bierzo: The Door of Forgiveness

Swim in the largest glacial lake in the Iberian peninsula, which is what it is mainly used for now

Work out the numbers: 3.47 square kilometres, 53 metres deep, cut by a glacier fifteen kilometres long

Find the moraine arcs downstream of the lake, which are the ice's terminal deposits

Look for striations and roches moutonnées on the rock around the shore

Walk up to the Laguna de los Peces above the lake, which is the same glaciation higher up

Sanabria is the largest glacial lake in the Iberian peninsula — 3.47 square kilometres at about a thousand metres, 53 metres deep in its deepest basin, gouged out during the Würm glaciation. The Tera glacier reaching what is now Ribadelago was nearly fifteen kilometres long and over three hundred metres thick, and it picked up the Cárdena and Segundera tongues on the way, which is what gave it the power to dig this hole. The ice went about twelve thousand years ago, apparently quite quickly, leaving hanging valleys, roches moutonnées, striations and concentric moraine arcs downstream.

Lago de Sanabria: A Glacier Left a Lake

Go into Gaudí's Episcopal Palace, built 1889–1913, and find out why he resigned from it in 1893 and never came back

Find the Roman ergastula and what is left of Asturica Augusta under the modern town

Go to the chocolate museum and work out how the railway turned a small León town into a chocolate industry

Buy mantecadas — documented here since 1805, sold as La Perla Astorgana from 1850, and still hand-wrapped by folding the paper a particular way

Eat cocido maragato, the only cocido eaten backwards: meat first, soup last, because that is the order the maragato muleteers ate it in at the roadside inns

Astorga began as a Roman camp for the Legio X Gemina in the late 1st century BC, became the civilian town of Asturica Augusta and capital of the Conventus Asturum, and had a bishop — Basílides — by the mid-3rd century. When fire destroyed the old episcopal palace, Bishop Grau commissioned a new one from his friend Antoni Gaudí; it went up between 1889 and 1913, and Gaudí walked off the job in 1893 after Grau died and the council began arguing with him. The town's other trade is chocolate, which arrived with the railway and built the modern place.

Astorga: Gaudí, Chocolate and Asturica Augusta

Climb to the keep of the 15th-century castle for the view over both rivers

Walk the walled village and work out that the roofs and the walls are the same slate

Work out why a frontier town was needed here and who it was facing

Drive up to the Lago de Sanabria, which is a short way up the valley

Go on into the Sierra Segundera, which runs into the Portuguese Montesinho

Puebla de Sanabria stands on a hill where the Tera and the Castro meet, with a 15th-century castle of the counts of Benavente on the highest point and a walled village of stone and slate below it — one of the best-preserved in this corner of Zamora, right against the Portuguese border. It was a frontier town for centuries and it looks like one. The Lago de Sanabria is a short drive up the valley, and the Sierra Segundera behind it runs into the Portuguese Montesinho.

Puebla de Sanabria: A Castle Over Two Rivers

Visit the Museo del Queso Manchego in Manzanares, Ciudad Real

Taste Manchego at three ages side by side: Semicurado (three weeks to four months), Curado (three to six months) and Viejo (one to two years), all made only from Manchega sheep's milk

Look for the embossed woven-esparto pattern on the rind, left by the traditional grass baskets

Buy an artesano Manchego, the label reserved for cheese made from raw milk

Manchego is made only from the milk of Manchega sheep, a breed that can live on the dry plateau of La Mancha, and it is pressed in moulds that leave a herringbone pattern on the rind — the mark of the esparto grass baskets it was traditionally wrapped in. The age is what changes it: semicurado is mild and springy, curado is firmer and nuttier, viejo at one to two years is hard, sharp and crystalline. Tasting the three side by side is the only way to understand why the label matters.

Manzanares: Manchego at Three Ages

See the Roman Theatre, built in 16–15 BC under Agrippa for about 6,000 spectators, and its 63m stage front; the International Festival of Classical Theatre has been held there since 1933

Cross the Roman bridge over the Guadiana, nearly 800m long

Visit the National Museum of Roman Art, where the theatre's original sculptures are kept

Walk out to the Acueducto de los Milagros, which carried water into Emerita Augusta

Mérida was Augusta Emerita, founded in 25 BC for veterans of Augustus's legions, and it became the capital of Lusitania — which is why a town of sixty thousand in Extremadura has the best Roman remains in Spain. The theatre was built in 16–15 BC under Agrippa for about six thousand people, and it has been used for a classical theatre festival every summer since 1933. The Roman bridge over the Guadiana is nearly eight hundred metres long. The Vía de la Plata, the old road north, runs right through it.