Colourful and quickly changing: graffiti can be considered the chameleon skin of any urban landscape (Curtis, 2005). Two millennia ago, people were already writing their thoughts on the urban surfaces of Greek Aphrodisias in present-day Turkey (Chaniotis, 2011) or Roman Pompeii in Italy (Garrucci, 1856), and this practice has lived on throughout many cultures until this very day (Lovata & Olton, 2015; McDonald, 2013). Because of this long history and the multitude of surfaces on which graffiti have appeared, defining ‘graffiti’ is complicated. A safe but overly general definition could be that graffiti are a multifaceted, ‘self-authorised’ (Blanché, 2015) form of personal mark-making that exploits the public space using a visual intervention. ‘Graffiti’ can thus be an umbrella term for many ancient and contemporary mark-making practices, including engravings, paintings, sprayings, stickers, and other personal expressions attached to public (urban) surfaces in legal or illegal ways. [Note that we use the adjective ’ancient’ instead of the commonly found ‘historic’ since the latter excludes prehistoric paintings and inscriptions from the graffiti definition. For more info on how to define ‘graffiti’, see Schlegel et al. in this volume].