Every tourist in Vienna is at some point directed to Michaelerplatz, a circular cobblestone plaza in the heart of the Austrian capital. Framed by a medieval church, baroque buildings and the modernist Looshaus, the site’s iconic architecture attracts hundreds of thousands of people a year.
Yet in the summer months, when the square’s pavement and lack of shade transforms it into a heat island, visiting isn’t always a pleasant experience. That’s why the City of Vienna moved to expand the area’s pedestrian zones and plant beds of grass and nine saplings before the end of 2024.
Which, in turn, triggered an uproar.
Furious architectural experts — including the country’s highest body in matters of monuments — warned that the renovation could jeopardize the historic center’s status as a world cultural heritage site. In a letter to the mayor that has since been signed by more than 400 experts, the writers contended that trees would block the square’s protected buildings and impede key sightlines. Signatories called on the city to cancel the plans, which had already been revised.
"The proposal to green Michaelerplatz is completely misguided, because such a redesign would destroy the identity of one of Europe’s most memorable squares," wrote Ákos Moravánszky, Professor Emeritus of Architectural Theory at ETH Zurich. "I also doubt that it would contribute significantly to the climatic redevelopment of the city center."
The controversy underscores a mounting challenge facing the world’s fastest-warming continent. As temperatures reach new heights, European cities must strike a balance between adapting to climate change and preserving sites of historical importance.
Planting vegetation is an appealing way forward, as tree canopies can reduce air temperatures by up to 5 degrees Celsius. Yet some conservationists are wary. UNESCO warned that Vienna’s plan, if not carefully executed, could have a "deleterious impact" on the capital’s cultural significance. The city center’s status as a world heritage site is already at risk because of plans to build a high-rise in the vicinity.
Vienna isn’t alone. The Ministry of Health placed Rome under its highest heat warning this summer, advising people to stay indoors during the hottest part of the day. But planting trees in many parts of Rome is practically out of the question, said Edoardo Zanchini, head of Rome’s climate office.
The authority responsible for heritage protection opposes trees at Piazza Navona or Piazza del Popolo — among the city’s culturally significant but unshaded squares — on the grounds that "changing their layout in even the smallest way can distort their value," a spokesperson for the office wrote in an email.
Of course, protecting monuments and adapting to climate change aren’t always at odds. Vienna plants around 4,500 trees a year without fuss, and the majority of the roughly 2,500 conservation-related requests sent every year to Austria’s Federal Monuments Office are "conflict-free," said Hanna A. Liebich, the organization’s head of architecture.
Paris, home of the Champs Elysées and Arc de Triomphe, is one example of a heritage-rich capital that’s also transforming itself into a model garden city. Since 2020, authorities have ripped out more than two acres of asphalt, planted over 100,000 trees and are now revamping a historical square, the Place de la Concorde.
Planting trees there was initially a no-go for Jean-Jacques Aillagon, chair of the redesign, who cited the square’s "strictly mineral" heritage. But he later acknowledged that greenery would both cool the city’s largest traffic roundabout and restore its original 18th-century look.
Still, the former culture minister cautions that there is no one-size-fits-all approach to dealing with heat. "We can’t implement this revegetation project in the same way everywhere," he wrote.
While Zanchini understands the perspective of cultural conservationists, he hopes to convince the decision makers in Rome to ultimately accept his view. "We need trees, shadow, water in public places where people live and tourists go,” he said. For now, the city plans to swap out asphalt with natural materials and install shading systems throughout the city, he wrote in an email.
Vienna found solutions too, implementing customized shading systems that act like sunglasses for buildings, and reviving a 19th-century system of air wells, deep underground shafts that draw in and cool fresh air before it flows through buildings.
In the case of Michaelerplatz, authorities are moving ahead with the roughly €8.5 million ($9.4 million) project, citing local support and close coordination with the Federal Monuments Office.
"People sometimes forget that people also live here. The city center isn’t just a historical showpiece," said Markus Figl, head of Vienna’s inner-city district.
Less than three months before the renovation is set to wrap up, digs, construction barriers and excavators still line the busy square. Tourists sip coffee in view of the chaos; the heat-tolerant ash and elm trees have yet to arrive.
Jürgen Furchtlehner, a senior lecturer at the University of Natural Resources and Life Sciences in Vienna, appreciates the city’s efforts to mitigate heat, but warned that there’s still much to do.
"I’m very much in favor of trees as a natural cooling measure, planting as many trees as possible, as comprehensively as possible," Furchtlehner said. "It’s important to do this not just selectively, not just for prestige projects, but to tackle the whole area."
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