Istanbul's Duplicate Image Problem: How the City Stacks Up Against Rome, Prague and Cairo

Istanbul's municipal digital archive holds more than 1.2 million photographs, a figure that has roughly tripled since 2019 — and by conservative internal estimates cited in a 2025 report by the Istanbul Metropolitan Municipality's Digital Heritage Unit, somewhere between 18 and 22 percent of those images are exact or near-exact duplicates. The problem is not unique to this city, but the scale and the stakes are particularly acute here, where heritage tourism generated roughly 12.4 billion Turkish lira in documented revenue in 2024 and where a single misattributed photograph of the Hagia Sophia or the Grand Bazaar can ripple across dozens of travel platforms within hours.

The issue has sharpened in 2026 for practical reasons. The Istanbul Metropolitan Municipality — controlled by CHP mayor Ekrem Imamoğlu's administration — launched its expanded open-data portal in March, making thousands of archival images publicly downloadable for the first time. That decision, welcomed by researchers and developers, also exposed a long-standing duplication backlog. Images tagged as "Kapalıçarşı interior, 1970s" sometimes appear under four or five separate accession numbers, occasionally with contradictory location metadata. At least one batch of photographs labelled as documenting the Sultanahmet district was found, after a spot check, to include images taken in Üsküdar on the Asian side of the city.

What Istanbul Is Actually Doing About It

Two organisations are leading the remediation effort. The Istanbul Research Institute, based in the Beyoğlu district on İstiklal Caddesi, has been piloting a perceptual hash deduplication system since January 2026 — a tool that compares images mathematically rather than relying on filename or metadata matches. The institute processes roughly 4,000 images a week through the system. Separately, TÜRSAB, the Association of Turkish Travel Agencies, issued new photographic sourcing guidelines to its members in April 2026, explicitly requiring that destination images used in marketing materials carry verified provenance tags before publication.

Neither initiative is fully solved. The Istanbul Research Institute's pilot covers only pre-2000 analogue-to-digital transfers so far, leaving more recent digital photography — the bulk of the problem — for a second phase planned for late 2026. TÜRSAB's guidelines are voluntary, and smaller operators along the Eminönü waterfront and in the backstreets of Balat have been slow to adopt them.

How Istanbul Compares to Rome, Prague and Cairo

Globally, the challenge of duplicate and misattributed urban imagery sits at the intersection of heritage law and platform governance, and cities are handling it very differently. Rome's municipal archive, the Archivio Storico Capitolino, completed a full deduplication audit of its 800,000-image digital holdings in 2023, reducing redundant records by roughly 31 percent according to a published project summary from the Comune di Roma. Prague's Institute of Planning and Development embedded deduplication checks directly into its public-facing image API in 2021, meaning duplicates are flagged automatically before they can be downloaded. Cairo's Egyptian Museum digitisation project, part of a broader UNESCO-supported programme, has taken a different approach entirely — prioritising human curatorial review over automated tools, which is slower but produces fewer false positives in collections where two photographs that look nearly identical may in fact document different restoration stages of the same artefact.

Istanbul's situation sits somewhere between Prague's technical efficiency and Cairo's curatorial caution. The city's heritage collection is vast, multilayered and politically complicated — images documenting Ottoman-era construction sit alongside photographs from the early Turkish Republic, and decisions about how to tag, classify and deduplicate them carry cultural weight that an algorithm alone cannot resolve. The earthquake risk factor adds urgency: since the 2023 Kahramanmaraş disaster, planners and emergency services have placed new importance on accurate visual documentation of structural conditions across Istanbul's older neighbourhoods, from Fener to Zeyrek, making duplicate or mislabelled building photographs a practical safety concern, not just an archival one.

The Digital Heritage Unit has indicated that a full deduplication roadmap for the open-data portal will be published by September 2026. For researchers, journalists and developers using the archive in the meantime, the institute recommends cross-referencing any downloaded image against the Atatürk Library's separate photographic database — a parallel collection that has been independently catalogued and covers much of the same historical ground with fewer duplication errors.