Urban spaces exist for human habitation: we live, work, and socialise within them, although at times we feel the need to escape the city. It is a kind of symbiosis. For millennia, human beings have needed urban spaces in order to function as societies and, at the same time, urban spaces exist as such only for as long as they are inhabited by human beings. Habitation is the form of the city, what animates it and makes it effectively a city. Urban space without human beings constitutes its matter, functionally structured and arranged to receive an organised collectivity. In our encounter with urban space and through our interactions within it, we constantly leave traces: elements, signs, and residues that speak of us while we are absent. Left on their own, these traces become clues to a past presence, stratifications of human identities and collectivities that are progressively absorbed into urban space until they become some of its defining elements. This sequence focuses on this presence of absence and on its accidental relation to urban space.