As I wait to meet my guide at the corner of one of Vienna’s market squares, I feel confident that I have already spotted what will be the first stop on our tour of the city’s ugliest buildings. The purple flowery facade of Leopoldsgasse 39 stands out from its beige neighbours, a beacon of individualism that I’m about to find is a common theme on this tour.

“It supposedly represents the artist’s love life,” my guide, Eugene Quinn, explains as we peer at lilac murals of crying women. “From the look of it, I don’t think it was very successful.”

Vienna is generally thought of as a handsome city: all imperial palaces and pretty squares. But a new tour launching – on 2 May, as part of Vienna’s Year of Walking Campaign, which will feature dozens of events to get people out on foot and a global conference, Walk 21, in October – aims to show an alternative to the fairytale cliches.

“The tour is meant to show a more gritty, urban, contemporary and humorous Vienna to outsiders – and perhaps also locals,” says Eugene, who runs the Ugly Walking Tour with co-guide Nina Hochrainer and a culture group called Space and Place. As we set off for a sneak preview, I find I enjoy many buildings for the same reasons others hate them. Dark histories, 1980s aesthetics, and modernism forced on top (literally) of 19th-century architecture, all tell interesting stories.

The gigantic Nazi anti-aircraft towers that loom over areas of the city escape the attention of many visitors. Photograph: Maddy French

One example, visible in nearly every neighbourhood, is the modern glass penthouse on top of an ornate, century-old apartment block. A product of Vienna’s increasing wealth, they’re a deliberate affront to the city’s traditional Altbau style.

“Their construction can cause years of disruption to neighbourhoods,” says Eugene. “It’s an example of how something can look OK by itself but clash horribly with its surroundings.”

Taste aside, these structures are interesting because they reflect a broader tension in Vienna between past and present. This is even more apparent in the historic centre, a Unesco-listed district that impresses visitors but is avoided by locals. Critics says that although Unesco status brings value, it restricts development. “So many decisions about the area are made in Paris. People end up self-regulating, and don’t bother building things,” says Eugene.

This district still has its fair share of ugly, including a Black Death memorial, background to countless tourist selfies, that is both gaudy and disturbing. And the six gigantic Nazi anti-aircraft towers that loom over areas of the city, though a fascinating insight into Vienna’s darker history, escape the attention of many visitors and are ignored by most tours.

Deciding whether you agree or disagree with Eugene and Nina’s choices – apparently, there were many to choose from – is part of the fun, and participants are invited to an ugly pub to continue the discussion afterwards. As Eugene says: “We want to start a debate with these tours, not finish it.”

• The tours start 2 May and cost €5pp, spaceandplace.at