A set of sunny posters with 100 unique designs created by fun-loving graphic design agency Studio Spass are currently peppered throughout the streets of Rotterdam, the Netherlands, promoting architectural festival Zig Zag City.

Rotterdam celebrates 75 years of reconstruction after WWII this week, and the festival highlights key examples of Dutch modernism. The posters aim to draw visitors to the Hoogkwaiter district, an area that was especially blighted during the blitz, and where blocky estates lined with steel pipe balconies have now come to define the urban landscape.

Studio Spass—which translates from German to ‘Studio Fun’—deals regularly with space and place; its favoured typographic installations energetically draw from things like a city’s overheard conversations or the shape of built environments. To capture the spirit of this year’s festival and its emphasis on architectural discovery, the agency used Gotham, as it had two years ago when creating the festival’s 2014 identity.

“We chose Gotham because of how the font was made by Tobias Frere-Jones’ expeditions, block by block, in search of the street typography secrets of old New York,” says studio co-founder Jaron Korvinus. “This story makes it such a good match for Zig Zag City; we felt like it was meant to be.”

A mustard yellow that’s so distinctive of modernism was chosen as the background color of the identity. It’s meant to reflect the spirit of the local architecture, specifically the mood of the square glass and concrete of Dutch architect Huig Aart Maaskant. “We also wanted to create a warm feeling as most of the festival’s activities are being held outside,” explains Korvinus.

No two people’s experience of exploring a city is ever the same, and reflecting these myriad ways to discover urban space was crucial to Studio Spass’ concept. “No matter how good your city plan is, people will always find or create their own path,” says Korvinus. The festival curated various routes to lead visitors through Hoogkwaiter, guiding them between different stop-off points of the programme—so there’s a zig zag of routes from the top floor of a key post-war building by Maaskant to the architectural intervention built by artist collective Numen, called Tape.

“We came up with an identity system that allowed us to draw a number of diverse routes on the posters, which visualize the number of ways of wandering during the festival,” says Korvinus. No single, simple poster would do.