ISUF 2026: How Outstanding and Universal Are World Heritage Cities?

For a while now, my days at MIT Senseable City Lab have revolved around one question: can you actually measure what makes a heritage city heritage? UNESCO inscribes places on the World Heritage List for their Outstanding Universal Value, a concept full of morphological connotations that has never been assessed systematically through the physical fabric itself. That is the gap the Heritage Signature project is trying to fill, and ISUF 2026 was the first time I shared its results with the urban morphology community.

The paper, written with Fabio Duarte, Ana Pereira Roders, and Carlo Ratti, takes the two words in the concept literally. Are World Heritage cities outstanding, meaning morphologically distinct from what surrounds them? And are they universal, meaning do they share a common spatial character across the globe? To find out, we analysed nearly half a million buildings across 60 UNESCO World Heritage properties, describing each one through the buildings, plots, and streets around it.

On the first question, the answer is a fairly confident yes. A Random Forest classifier, tested each time on a site it had never seen, can tell heritage fabric apart from its immediate context. What gives heritage away is finer grain, better connected streets, more enclosed streetscapes, and a more heterogeneous composition. On the second question, the answer is more interesting than yes or no. Heritage sites fall into seven morphotypes that cut across regional boundaries, from courtyard compounds and fine-grain medieval towns to regular colonial grids and terrain-adapted hillside settlements. Universality, it turns out, looks more like structured diversity than sameness.

I presented the work at ISUF 2026, the International Seminar on Urban Form, hosted by Pontificia Universidad Católica de Chile in Santiago under the theme "Intelligences and Realities." A full paper is in the making.