Coimbra is Portugal's city of dreaming spires, even if its Romanesque architecture tends towards rounded arches and square towers. Yet the country's oldest seat of learning has its work cut out in the destination stakes. The stats are calming rather than scintillating. Population: 150,000. Unique selling point: a beautiful hilltop campus founded before Oxford or Cambridge. Nightlife: cafés and disco-bars. Repeat: disco-bars.
Coimbra has the air of a gracefully arranged secret. Its seemingly low-key attractions, in a town with a wonderfully relaxed atmosphere, have been potent enough to attract half a million visitors a year, mainly from Spain, Germany and Italy. Yet within three years, its mayor, Carlos Encarnacao, told me, Coimbra will be transformed into a destination that will lure many thousands more tourists away from the obvious urban magnets of Porto and Lisbon.
A familiar first step has been taken to kick-start the process. In November, Coimbra took possession of a bona-fide architectural icon, a footbridge designed by Cecil Balmond of Arup, assisted by the Portuguese engineer, Adao da Fonseca, whose own Ponte do Infante is one of Porto's star architectural turns.
Balmond's technically brilliant 300m span across the Rio Mondego embodies a tenderly bizarre moment in Spanish history that seems like a hallucinatory outtake from a Luis Buñuel or Pedro Almodovar film. When Encarnacao opened the bridge, he named it the Ponte Pedro y Ines. Pedro, son of King Afonso IV of Portugal, was forced into a marriage with a Castilian princess, Constanza, but fell in love with her lady-in-waiting Ines de Castro, and the affair lasted until Constanza's death in 1345. At this point Afonso sent three men to murder Ines.
Pedro is said to have had Ines's body exhumed in Coimbra and placed on a throne at the monastery of Santa Maria at Alcobaça, south of Coimbra. He then forced his vassals to kiss the hand of the deceased "queen". Pedro and Ines's tombs face each other across the monastery's transept. Inscribed on them are the words: "Até o fim do mundo." ("Until the end of the world.")
This is the beginning of Coimbra's new world, perhaps. Standing on the new bridge-cum-metaphor, it's easy to see that, by connecting the right bank of the Rio Mondego - the town beneath the hilltop campus - with the left bank, café-society is arriving fast. The new riverside park and restaurants on the right bank will be mirrored by landscaping and a sylvan promenade on the left.
Coimbra's new icon looks rather svelte, but Balmond's search for a romantically-charged "vanishing point" at the centre of the Ponte Pedro y Ines was fraught. His solution: a platform at the mid-point, putting a kink in the structure that casts shadows several metres along the side of the bridge's deck. From the north bank of the Mondego, the pale grey line of the span does indeed seem to waver on the edge of invisibility.
I found the zig-zag railings - inset with coloured, angular, glass panels - even more intriguing. They are lit at night to produce the effect of a luminous ribbon floating above the river. It is a touch of Paul Klee-like artistry in a town where art has usually glorified learning and religious faith. That deference is hardly surprising, for Coimbra's character and beauty lie in the layers of its history. This, then, is a town to walk, having donned grippy trainers that can cope with the very smooth marble and basalt cobbles of the town centre on the north bank; we're talking urban hill-walking.
But don't take fright. Coimbra is about half the size of Brighton, which means its key vistas and historic sites can be absorbed over a couple of ambulatory, café-punctuated, days. It strikes me as an ideal place to either break a touring holiday in Portugal, or to escape to from the hurly-burly of Porto or Lisbon, both about an hour away by train. The air is very fresh - there's no industry here - and the vibe calmly gregarious.
The problem, if there is one, is planning what to see in a place of such rich provenance. Established as Aeminium by the Romans around 100AD, it was then dominated by Germanic invaders, who gave way to the Moors in the eighth century. Not until 1064 did Ferdinand the Great put Coimbra under permanent Portuguese rule.
In the face of such complexity, I took a top-down approach. Immediately, and foolishly, I headed up the stairs from the Rua da Alegria, which rose at 45 degrees and took two minutes to scale: a shortcut to the university plateau, or alta, that was more like a cardio-MOT test. From the top, I took in the university buildings and the views to the river and the convents of Saint Francisco and Santa Clara beyond it. From here, it was more than agreeable to slalom slowly down the streets and alleys to the lower town, where the Mannerist-cum-Baroque façade of St John of Santa Cruz church stopped me in my tracks.
If you take a slightly different route, down the Rua Olimpio Nicolau Rui Fernandez, you'd encounter the equally extraordinary 12th-century Jewish Fountain.
Even armed with a map, I lost my intended route twice - and it was a pleasure to do so. How else would I have found myself looking up at the Ship House in the Rua da Ilha? Its architecture - it was hot, I may have been hazily dehydrated - managed to remind me of Gaudi, Erich Mendelsohn's modernist Einstein House, and something from the Brothers Grimm.
However, no building is fuller of Coimbra's sediments of history than the Old Cathedral. The 12th-century building is rooted in the remains of earlier churches, including a Moorish mosque. I loved its ambiguities - the chunky, fortress-like elevations, the complex tracery of the altarpiece, and the cloisters' air of Da Vinci Code mystery.
As for the campus, there are two ways to deal with it. Option one: a day's ferreting through almost 30 specific historic sites on the alta. Option two: the Merrick three-pack (after buying a €4.50/£3 multi-pass in the main university library). First up, the stateroom; then St Michael's Chapel, whose decorative encrustation took three centuries to complete; finally, a real showstopper, the early 18th-century Joao V Library.
The historical density of the lower town is less obvious, but the streets to the west of the Rua Visconde da Luz and the Rua Ferreira Borges - the main "posh" shopping avenue - retain the air of an arcane maze; and this part of Coimbra will, within three years, be revivified. Many of the older streets and terraces in the town are visually delightful, but their atmospheric charm typically conceals very basic domestic amenities. Not for long, though. It's a kind of gentrification, or as the Portuguese put it, reabilitada de la moda. Not that Coimbra risks becoming exactly modish. Its charms are probably unique in Portugal, and proof against the tides of touristic fashion. Its urbane, quietly romantic atmosphere will remain unruffled - even by the architectural icon that now crosses the Rio Mondego.
The writer flew to Porto with TAP Portugal (08456 010 932; www.flytap.com), which flies from Heathrow and Gatwick. Ryanair (08712 460 000; www.ryanair.com) flies from Liverpool and Stansted. There are flights to Lisbon with TAP, BA (08708 509 850; www.ba.com) and Monarch (08700 405 040; www.flymonarch.com). To reduce the impact on the environment, buy an "offset" from Climate Care (01865 207 000; www.climatecare.org). The environmental cost of a return flight from London to Lisbon is £2.60. There are regular fast trains to Coimbra from both Porto and Lisbon (00 351 213 185 990; www.cp.pt).
Le Méridien Park Atlantic, Porto (00 351 22 607 2500; www.starwoodhotels.com). Doubles from €80 (£57), room only. Quinta das Lágrimas, Coimbra (00 351 239 802 380; www.quintadaslagrimas.pt). B&B from €142 (£101). Hotel Dona Ines, Coimbra (00 351 239 855 800; www.hotel-dona-ines.pt). B&B from €75 (£54).
EATING & DRINKING THERE
O Porquinho, Coimbra (00 351 239 494036). Quinta da Romeira, Coimbra (00 351 239 781 301). Quebra Club, Parque Verde do Mondego, Coimbra (00 351 239 836 038). Café Santa Cruz, Coimbra (00 351 239 833 617).
Portugal Central Tourism: 00 351 239 488 120; www.turismo-centro.pt