Walk in through the successive gates strung along the neck and work out that there is no other way in

Look down at the Júcar and work out how nearly the loop closes

Work out why the place was called impregnable, and that Alfonso VIII still took it in 1184

Go into the 8th-century Muslim castle at the end of the spur, a parador since 1966

Count the churches in a village of a few hundred people and work out what that implies

The Júcar loops almost completely round the promontory Alarcón stands on, which made the place effectively impregnable — the castle is Muslim work of the 8th century and Alfonso VIII took it in 1184. The way in is still through successive gates strung along the neck of the meander. The castle at the point of the spur opened as a parador in 1966 and is now what the town largely lives on. The village inside the walls has a few hundred people and four churches, which tells you what size it used to be.

Alarcón: A Fortress in a River Loop

Walk round the upper lagoons — the Gitana, the Tejo and the little Tejo — and name the colour of each

Look down into the lagoons from the rim and work out how a collapsed sinkhole fills with groundwater

Walk among the Torcas de los Palancares, the dry sinkholes of the same geology

The lagoons of Cañada del Hoyo are seven karst lakes — five lagoons and two smaller lagunillos — in the Palancares hills 40 kilometres from Cuenca, fed from underground and by rain, and a Natural Monument since 2007. Each looks a different colour because of microorganisms, submerged plants, the light and the season, though a glass of water from any of them is clear: the Tejo is dark blue, the little Tejo black, Cardenillas sky blue, the Parra blue. The Gitana was blue too, and has been green since the 1980s from the number of people bathing in it. Their levels drop a little every year as the aquifer is pumped. Eight kilometres away the Torcas de los Palancares are the same sinkholes without the water.

Cañada del Hoyo: Seven Lagoons, Seven Colours

Work out the dating from the coats of arms — the third wife of 1472 is not on the building anywhere

Find where the design accommodates artillery, which was a new problem in the 1450s

Work out that this is a palace as much as a fortress, and where one becomes the other

Find out who Eugenia de Montijo was and why an empress of the French restored a castle in Cuenca

Go down to the collegiate church in the village, which Hanequín de Bruselas also worked on

Juan Pacheco, first Marquis of Villena, started this castle on the Cerro de San Cristóbal in 1455 and the work ran to about 1468 — you can date it from the heraldry, because his third wife, married in 1472, appears nowhere in it. Hanequín de Bruselas was the architect, and Juan Guas probably finished it. It was built as a fortress-palace and specifically adapted for the coming of artillery, which was a new problem at the time. Eugenia de Montijo, empress of the French, inherited the house of Villena and restored it.

Belmonte: A Castle Built for Artillery

Walk to the Casas Colgadas, the 15th-century hanging houses overlooking the gorge of the Huécar

Visit the Museum of Spanish Abstract Art in the Casas Colgadas, established in 1966 by Fernando Zóbel

Visit Cuenca Cathedral, known as the first Gothic cathedral in Spain thanks to Anglo-Norman influence

Walk the old town on its narrow escarpment between the Júcar and Huécar rivers, a UNESCO World Heritage Site since 1996

Cuenca is built on a spit of rock between two river gorges with nowhere to expand, so it built outwards over the edge — the Casas Colgadas hang off the cliff above the Huécar on wooden balconies, which is a 15th-century solution to a housing shortage. In 1966 Fernando Zóbel put the Museum of Spanish Abstract Art inside them, which turned out to be an inspired pairing, and the old town went onto the World Heritage list in 1996. The cathedral is claimed as the first Gothic in Spain, built with Anglo-Norman influence.

Cuenca: Hanging Houses and Abstract Art

Walk the circuit and work out that every shape in it was cut by water out of a seabed

Work out the sequence: Tethys seafloor 90 million years ago, lifted by the alpine orogeny, then karst weathering ever since

Find the fossils in the rock, which are the direct evidence of what this was

Work out why it was protected as early as 11 June 1929, which is very early for a Spanish natural site

Go on into the wider Serranía de Cuenca and find the Ventano del Diablo over the Júcar gorge

Ninety million years ago this was the floor of the Tethys sea. The alpine orogeny at the end of the Cretaceous lifted it out of the water, and karst weathering since has cut the limestone into freestanding blocks, mushrooms, corridors and arches at 1,500 metres among pine forest near Valdecabras. It was declared a Natural Site of National Interest on 11 June 1929 and now sits inside the Serranía de Cuenca natural park. The land is private and there is a modest entry charge, which is worth knowing before you drive out.

The Ciudad Encantada: A Cretaceous Seabed, Weathered

Stand on the bridge and look up at a village built into the wall of a river meander

Climb to the Almohad castle of the 12th or 13th century on the rock above the houses

Go into one of the cave houses and find the ones that go right through the ridge and out the other side

Work out what the name means and what it tells you about who built the place

Walk or swim the Júcar below the village, which is what the gorge is for in summer

The Júcar has cut a meander so tight into the Albacete plateau that the village of Alcalá del Júcar is built on both the inside of the bend and up its wall, with an Almohad castle of the 12th or 13th century on the crag above. The houses are pushed back into the soft rock — some of them run right through the ridge and come out as windows on the far side — and several of the cave houses are open to go into. The name is from the Arabic for castle: the castle of the river Júcar.

Alcalá del Júcar: A Village Dug Into a Gorge

Sit in the theatre and find out which local family paid for it and what they had made their money from

Work out what lapis specularis was and why translucent gypsum was worth that much to Rome

Walk the amphitheatre and the forum, both finished by the end of Vespasian's reign

Go to one of the lapis specularis mines in the area and see where the sheets came out of the ground

Work out what happened to the town — the population simply moved three kilometres to Saelices, next to the spring

Pliny records that Segóbriga mined lapis specularis — translucent selenite gypsum, split into sheets and used as window glazing across the Roman world. It made the town rich enough that some local families put senators into Rome. Manius Octavius Novatus, son of a praefectus fabrum of the same name, paid for the theatre; his cognomen survives in the place name Noheda, where his family's villa was. By the end of Vespasian's reign the theatre and amphitheatre were finished and the town was fully integrated into the empire. After the reconquest the population moved three kilometres north to Saelices.

Segóbriga: The Town That Glazed Rome's Windows

Go underground into the workings and work out what mercury mining actually did to the people doing it

Learn the Arabic words still used here — azogue, jabeca, aludel — and what each one means

Work out the chain: mercury from here refined American silver, and American silver paid for the empire

Find out what the Real Cárcel de Forzados of 1754 was for and who was in it

Find out that penal labour detachments were still working here in the 1940s

Work out why UNESCO listed Almadén and Idrija together in 2012

Almadén sits on the largest cinnabar reserves in the world, and they were being worked when Strabo, Vitruvius and Pliny wrote about them. The Arabic vocabulary still used in the mines — azogue for mercury, jabeca for the furnace, aludel for the pipe, and almadén itself, meaning the mine — records who ran them next. Mercury was essential to the silver refining that funded the Spanish empire, and the work was done substantially by convicts: the Real Cárcel de Forzados was built here in 1754, and penal labour detachments were still operating in the 1940s. UNESCO listed the mines in 2012 alongside Idrija in Slovenia.