Walk the cloister and work out that it is on the outside of the church, looking out over the plain

Climb the octagonal bell tower for the view over Lleida and the Segrià

Work out what the bare interior means: this was a barracks for more than a century after Philip V took it

Find the carved capitals that survived the conversion, and the ones that did not

Look down at the modern city and work out why the cathedral is up here and nothing else is

The old cathedral of Lleida stands on the hill above the city with a cloister on the outside of the church rather than tucked behind it — an open arcaded gallery with a view over the plain, which is unusual to the point of being unique. After the War of the Spanish Succession Philip V turned the whole complex into a military barracks, and it stayed one for well over a century, which is why the interior is bare. It was slowly recovered in the 20th century. The octagonal bell tower is one of the tallest Gothic bell towers in Catalonia.

La Seu Vella: A Cathedral Used as a Barracks

Stand under the royal tombs raised on arches across the transept — the pantheon of the Crown of Aragon

Walk the cloister and work out what the Cistercians were actually after: water, isolation and farmland

Find the monks' dormitory, which is one of the largest surviving Cistercian dormitories anywhere

Work out the founding: given to monks from Fontfroide in 1149, community established 1153

Remember that this is a working monastery again, and that some of what you cannot see is why

Ramon Berenguer IV gave this site to Cistercian monks from Fontfroide in 1149 and the community was established under its first abbot in 1153 — it met everything the order asked for in a foundation: isolation, plenty of water and land to farm. It became the royal pantheon of the Crown of Aragon from the end of the 14th century until the royal house died out, and it is the prototype of the Spanish Cistercian abbey. UNESCO listed it in 1991. Cistercians live in it again, so parts of it are enclosure and closed to visitors.

Poblet: The Royal Pantheon of the Crown of Aragon

Find what is left of the castle, the last Muslim stronghold in Catalonia

Go into the Romanesque church of Santa Maria de Siurana

Look down from the cliff to the Siurana reservoir far below

Siurana is a hamlet of a few dozen people at about 740 metres on the edge of a limestone cliff at the end of the Prades mountains, above the Siurana river. Its castle, on a rise in front of the village, guards the only natural way in, and the Christian walls are built over a Muslim fortress: Siurana was the last Muslim stronghold in Catalonia, taken by Ramon Berenguer IV's forces in 1153–1154 after a siege, some years after Tortosa and Lleida had fallen. The Romanesque church of Santa Maria stands in the village, and the Siurana reservoir lies far below, at about 470 metres.

Siurana: The Last Muslim Stronghold in Catalonia

Visit the ruins of Scala Dei Charterhouse, founded in 1194, whose Carthusian monks introduced viticulture to the region and gave Priorat its name from the prior's authority over seven villages

Taste a Priorat DOQ wine in Gratallops, where René Barbier and Álvaro Palacios led the region's revival in the 1980s

Walk the terraced vineyards on llicorella, the black and red slate soil laced with mica that forces the Garnacha and Cariñena vines deep

Carthusian monks founded Scala Dei in 1194 and planted vines, and the priory's authority over seven villages gave the region its name — Priorat. The soil is llicorella, black and red slate shot through with mica, which holds almost no water and forces old Garnacha and Cariñena vines to send roots metres down to find it. The result is concentrated and expensive. The region had all but died by the 1970s; René Barbier, Álvaro Palacios and a handful of others revived it in the 1980s, and it is now one of only two DOQ regions in Spain.

Priorat: Scala Dei and the Llicorella Vineyards

Visit the Parc Astronòmic Montsec near Àger and observe through the observatory telescopes — the facility operates public observation sessions under some of the darkest certified Class 1 skies in Catalonia

Walk the Congost de Mont-rebei gorge — the Noguera Ribagorçana river cuts a 500m canyon through the Montsec range, accessible only on foot along a clifftop path with sections of fixed iron ladder

Look for griffon vultures nesting in the Montsec cliff faces — colonies of 80+ pairs nest in the gorge and ride thermals above the observatory plateau throughout the day

Visit Sant Miquel d'Àger collegiate church and photograph the Romanesque apse against the dark pre-Pyrenean sky at dusk

A Class 1 IDA Starlight Reserve — the highest designation — in the Catalan pre-Pyrenees, where a world-class dark sky observatory sits above a gorge accessible only on foot and griffon vultures nest in the canyon walls below

Montsec: A Starlight Reserve Above the Mont-rebei Gorge

Walk the Gothic cloister and work out how much carving a Cistercian house was supposed to permit

Find out who Reinard de Fonoll was, what an English mason was doing in 14th-century Catalonia, and what was demolished to let him build

Find the royal pantheon built for Peter III the Great, and the tombs of James II and Blanche of Anjou

Find the abbot's rooms James II turned into a royal palace, and the walls Peter IV threw round the lot

Do the Ruta del Císter properly and add Poblet and Vallbona de les Monges

Santes Creus is the second of the three great Cistercian houses of the Catalan Ruta del Císter, with Poblet and Vallbona, and the one with the finest Gothic cloister — built by the English master Reinard de Fonoll with Guillem de Seguer after James II had the Romanesque cloister pulled down to make room for it. Peter III the Great asked to be buried here and the royal pantheon was built for him in the 13th century; his son James II and James's queen Blanche of Anjou lie here too. James also turned the abbot's rooms into a royal palace, and Peter IV walled the whole place. The monastery is unusual in having a village living inside its walls, in the buildings the community left behind.

Santes Creus: The Other Cistercian Pantheon

Walk along the top of the channel and work out that nothing in the structure is mortared

Work out the fall — forty centimetres over 217 metres, which is what kept the water moving

Stand underneath and look up 27 metres at two tiers of arches

Work out where the water was coming from: twenty-five kilometres away, along the Francolí

Find out why it is locally called the Devil's Bridge, which is a common name for Roman work nobody could explain

Four kilometres north of Tarragona, in pine woods off the old road, a Roman aqueduct arcade stands almost intact: 217 metres long, 27 metres at its highest, two tiers of arches in dry-jointed ashlar with no mortar anywhere in it, and a fall of forty centimetres from the north end to the south to keep the water moving. It carried water twenty-five kilometres into Tarraco along the Francolí. Locally it is the Pont del Diable, the Devil's Bridge, because a Roman structure that good in the middle of a wood needed explaining.

The Ferreres Aqueduct in the Woods

Go into the Cau Ferrat and work out that the wrought iron collection is the reason the house is called that

Find the two El Grecos Rusiñol paraded through the streets when he brought them here

Work out what the Festes Modernistes from 1892 were for and what came out of them

Go next door into the Maricel and out along the seafront the pair of them face

Come for Carnival in February, which is one of the biggest in Catalonia

Santiago Rusiñol bought two fishermen's cottages on the seafront at Sitges, knocked them together and made the Cau Ferrat — part studio, part museum of the wrought iron he collected, and the venue for the Festes Modernistes from 1892, where Catalan Modernisme was effectively launched as a movement. Two El Greco paintings hang in it, which he carried through the streets in procession. Next door is the Maricel, and the town behind is a compact white grid on a headland. Sitges also has one of the largest carnivals in Catalonia and is a long-established gay resort.

Sitges: The Town Modernisme Was Argued Out In

Go into the crypt and look at the leaning brick columns, none of which is vertical

Work out why the columns lean: they follow the line of force, so nothing needs buttressing

Find the hanging chain model and work out how Gaudí designed a building upside down

Walk the colony around it — the houses, the school, the co-operative — built by Gaudí's collaborators

Work out what was never built here and how much of it went into the Sagrada Família instead

Eusebi Güell built a textile colony outside Barcelona with houses, a school, a co-operative and a cultural centre, and gave Gaudí the church. Gaudí did the site planning with Berenguer, Rubió and Canaleta, and designed the church himself — but only the crypt was ever built, because Güell died in 1918 and his sons dropped the project. That crypt is where Gaudí worked out the leaning columns, the branching structure and the hanging chain models that the Sagrada Família is built on. Everything he later did at scale was tested here first.