The purpose of this paper is to analyse urban transformation as a tourism resource. Tourism is undeniably a powerful motor for urban transformation but in return, urban transformation can represent a resource for actors related to tourism. More precisely this paper focuses on one major transformation of modern cities: gentrification. The central hypothesis of this paper is that gentrification accompanies tourism, but that gentrification itself may also become an object of the tourist gaze. The paper focuses on local guides and small touristic entrepreneurs in order to identify the tensions that might arise. The presentation of two guided tours – “Subculture Brixton Nightlife Tour” and “Where Brooklyn At?” – will enable us to explore how the gentrification of Brixton (London) and Brooklyn (New York) may be used as a tourism resource for local private entrepreneurs. Results presented here are based on ethnographic methods such as observation as well as content analysis and semi-directive interviews. Mobilising the historical concept of “slumming”, this paper proposes an extended conceptual framework, “neo-slumming”, to analyse evolving tourism practices in modern cities, practices that are considered here as tourism's new frontiers. However, as tourism transforms cities, the process itself is now of interest to tourists and thus becomes a resource for sector businesses (Naef, 2018). Yet studies about the touristification of urban transformation are still quite rare. This analysis aims to fill this gap by looking at the way a process, such as some spectacular, rapid or radical transformation of the urban fabric, can become a touristic resource associated with specific narratives and representations. In this context, the tourist gaze (Urry, 2002) is directed on a resource characterised by its ongoing change.