In the heart of Cologne, where modern life hums along the sidewalks, small brass plates embedded in the cobblestones silently mark the past. These Stolpersteine carry the names of victims of the Nazi regime and are located at the places where they once lived freely — before everything was taken from them. With over 100,000 plaques across Europe, they form the largest decentralized memorial in the world. And yet, they often disappear from view in the hustle and bustle of everyday life.

That changed in 2022 when WDR, one of Germany's largest public broadcasters, launched its successful “Stolpersteine NRW” project. Since the launch of the app in January 2022, users have been able to explore historical sites through augmented reality (AR) remembrance tours. In 2024, WDR expanded this experience in collaboration with Berlin-based startup ZAUBAR to include an interactive AR feature — and thus introduced a new, immersive form of remembrance that builds on the original concept. ZAUBAR’s software component further improved the AR functionality and user engagement.

At the former headquarters of the Cologne Gestapo — now home to the NS Documentation Center — visitors can experience five short AR tours directly on their smartphones. These multimedia experiences combine vivid 3D illustrations, historical photographs, and short audio clips, seamlessly integrated into the live camera view and surroundings. This creates a powerful moment of presence: the past is laid directly over the present.

The app now offers two different AR modes. The first is location-based. At places like the NS Documentation Center in Cologne, users can explore where history happened. These tours do not focus on individual Stolpersteine, but on the broader context of persecution and resistance at these locations. Additional AR experiences for other key locations in North Rhine-Westphalia, particularly places related to deportations, are already in development.

The second mode is location-independent and centers on the Stolpersteine themselves. Here, users can select a specific Stolperstein and virtually place it in front of them — whether at home, in the classroom, or elsewhere. They can even light a virtual candle next to it to create space for personal reflection — regardless of location. This remembrance feature expands the possibilities of commemoration beyond physical boundaries.

ZAUBAR, a Berlin-based startup, supported WDR in the technical development of the AR features. Although the AR content is only part of the app, it plays a significant role in deepening the user experience. In close collaboration with WDR, ZAUBAR brought in its expertise in location-based AR to ensure that each scene feels authentic and grounded. A visual positioning system is used to precisely align digital content with real-world environments.

It is important that Stolpersteine NRW was designed to be inclusive and accessible. Screen reader compatibility, intuitive navigation, and a guided tutorial provide users from diverse backgrounds with full access to the experience. The app also saves user progress, allowing for flexible exploration at one’s own pace.

For educators and younger audiences, the app transforms remembrance into a tangible, real moment. By combining journalism, storytelling, and interactive media, WDR and ZAUBAR have created something that is more than just an app — it is a bridge between generations.

At its core is a shared goal: to use technology not to distract from history, but to bring it closer. Through thoughtful collaboration, WDR and ZAUBAR have turned Stolpersteine NRW into a living archive — where once nearly forgotten stories can be remembered in a personal and powerful way.

The app is available for iOS and Android — more cities and stories will follow soon. Because remembrance is not just about looking back — it is about carrying memory forward.

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