If you decide to spend a night at Coimbra’s Monastery of Santa Clara-a-Nova in the near future, do bear in mind that the place is almost certainly haunted. Disembodied children’s voices echo around the first floor of the 17th century convent perched atop a hill in the Portuguese university city, overlooking the medieval centre from across the Mondego river.

In the garages, dry foliage has been arranged in geometric shapes, as if in preparation for a wicca ritual. You need the nerves of a ghost-hunter to walk through the pitch-black ground-floor corridor of the dormitory wing, lit only by a neon strip at either end, where tortured wails ambush you from the monkish cells. Sung in Albanian, Chinese, Kurdish, Kyrgyz and Turkish, these laments are part of an installation by US artist Taryn Simon, but they feel like spectral reminders of the nuns who lived in these quarters for two centuries.

After the last nun died in 1891, Santa Clara-a-Nova served for almost a century as a barracks for the Portuguese army, and since 2015 the nunnery has been the central hub of Anozero, a biennial art festival that sees its 9,650 sq metres filled for three months with works by creatives from around the world. But as the government has recently granted a private company the right to develop the semi-derelict building into a hotel, that arrangement could soon come to an end.

“You can have people living here, but it should be around art,” Anozero’s co-founder and director Carlos Antunes tells me outside a make-shift bar in Santa Clara’s luscious gardens on the eve of festival’s opening. He threatens to pull the plug on the festival if plans to revamp the convent as part of the Portguese government’s Revive programme go ahead in their current form. “I don’t have a plan B. This is my fight. If the biennale gets cancelled, it will be a huge problem for the city.”

With that in mind, this year’s ghostly edition of the festival can be read as a warning to the developer taking custody of the building: these spirits will give sleepless nights to your investment bankers on their golf holidays, Simon’s installation seems to whisper. But given art biennials’ own complicated relationship to gentrification, it is whispered for a reason.

The concept of a city hosting an international art exhibition at regular intervals goes back to the first Venice Biennale of 1895, when the capital of Veneto sought to rejuvenate the Italian art market after the decline of the Grand Tour tradition. The festival brought in visitors who would later return as tourists, while also granting the local population access to artworks of international renown and giving curators a freedom to experiment that institutions would rarely allow them.

In the 1990s, fuelled by cheap air travel and politicians chasing the Bilbao effect, every city wanted its own biennale. As well as blockbuster events such as Kassel’s Documenta, New York’s Whitney Biennial and the Bienal de São Paulo, there are now more than 200 such festivals across the world, from Andorra to Yokohama.

But with the boom came backlash: the suspicion that biennales were above all an excuse for a tote-bag-wearing international art crowd to descend on a city for a few weeks, leaving behind a large carbon footprint but little meaningful engagement with the local population. “Can the Biennial Serve a City, or Just ‘Big Art’?” Artforum magazine asks in its current issue, dedicated to the biennale identity crisis.

Worse still is the suspicion that art biennials serve as a handmaiden rather than a hindrance to gentrification. In some cases, they have brought to life forgotten spaces that went on to become permanent art institutions, such as the former margarine factory that is now Berlin’s KW. In others, they lent a sheen of cool to buildings that were then pounced on by developers. Squatters living in a disused rail shed in Lagos were evicted after it served as the site of the the inaugural 2017 biennale in the city.

Despite having only been around since 2015 and operating on a relatively modest budget of €800,000 per edition, Coimbra’s Anozero has been at the forefront of art festivals trying to rethink the format. A 2023 manifesto stated that biennales should no longer simply be “places to catapult artists and modes of visual production”, but experiments in communal living and thinking, dreaming up new uses for historical sites. “In Portugal, we have a tendency to live on old glories,” says Antunes. “The biennial is meant to be a door to the future”.

This year, Anozero proposes a new remedy for biennale fatigue: anarchism. Its title, Segurar, dar, receber (“To hold, to give, to receive”), may dip into the jargon of therapeutic healing and expressive fragility so fashionable with contemporary curators. But it turns out to be inspired by Peter Kropotkin, the Russian anarchist philosopher. Anarchism here does not mean anarchy but co-operation: Kropotkin’s big idea was that mutual aid was more central to evolution and civilisational progress than Darwin’s idea of the survival of the fittest.

Anozero receives funding (from local municipalities and Coimbra University), but it also tries to give back. For the opening, Portuguese artist Vasco Araújo led a delegation of 260 singers, all dressed in white and drawn from local choirs and music groups, on a march from Coimbra’s central square to the convent, while singing a chorus from Verdi’s opera Nabucco – a pied-piper march designed to lead the townsfolk up to the temple of contemporary art.

There are works here that could be classified derivatively as “festival art” – variations of Taryn Simon’s installation Start Again the Lament have been put in situ at the Park Avenue Armory, New York, the Cisternerne at the Frederiksberg museum in Denmark and a secret crypt beneath Islington Green, London. But at the Santa Clara nunnery it manages to gain potency through the oppressiveness already inherent in the architecture. It lives up to its manifesto promise to create art “which can only happen here and nowhere else”.

Once you emerge out of the darkness at the end of the long corridor, you can descend down brittle stone staircases into the gardens, where Amsterdam-based architectural designers Inside Outside have freed from weeds what may once have been a washing area, planted citrus and kumquat trees that will grow over the coming years, and set up chairs as to “encourage conversations with strangers”. “We understand that the biennale is an attempt to keep the convent grounds accessible to the public,” says Inside Outside’s Aura Melis. “So we tried to create something that will still be here in two years’ time.”

The intentions are laudable, but for now all they have to show are a table and some empty chairs, and unless Anozero manages to succeed in stopping the hotel development, the same space could well accommodate a swimming pool before the kumquat trees bear their first fruit.

At times, the biennale seems unsure of how forceful a gesture of protest it wants to strike. In two of the cells, curators have set up twin beds in which visitors can stay overnight and watch two long experimental films, Belgian director Chantal Akerman’s La Chambre and Finnish artist Juha Lilja’s Sleep. A parody of the Santa Clara’s imminent hotelification? Or a trial run for a compromise? The wall text merely calls it an “allusion” to Santa-Clara’s “uncertain future”.

Coimbra is home to one of Europe’s oldest universities and if you walk up or down its steep cobbled streets, you pass students in old-fashioned gowns, some carrying large wooden spoons in keeping with age-old student traditions. But it also has a long history of protest culture. The city is unique in Europe for having more than 20 leftwing and anarchist fraternities, known as repúblicas. With poetic names such as Republic of Ghosts and Palace of Madness, these self-managed communal housing projects offer shelter and food for students from disadvantaged backgrounds, as well as welcoming rites for first-years that are more gentle than the hazing rituals practised by more conservative students. They are places that put mutual care into practice.

Given Anozero’s anarchist theme, there’s an obvious connection to be made here – some of the repúblicas are directly outside the festival’s venues, and many students who live in them work behind the scenes of the biennale. But they are oddly absent from what is put on display. Instead, the curators have filled rooms of the nunnery with books on anarchist town planning in display cases and flow charts showing Kropotkin’s influence on important architects.

On opening day, two república veterans have made the trek up to the hill. Jaime Miranda, 53 and João Paulo Bernadino, 57, stand out amid the stylish art crowd. “The biennale attracts a certain elite,” says Miranda. “Young people who live in the repúblicas don’t usually get invited here.” But they are glad they made the trip. “Now I understand why there are determined to stay here,” he says, marvelling at the building complex. The housing project where they used to live, Real República Boa-Bay-Ela, once too faced an uncertain future. When Portugal’s rental law changed, the students faced eviction. Former inhabitants reacted by clubbing together and buying out the landlord.

For its next edition in 2028, Anozero is teaming up with Manifesta, the nomadic cultural biennale that travels to a different location in Europe every two years. To ensure it won’t be the last one, they could do worse than learning from the locals.