« There is no civilisation without memory, there is no society without ruins », argues Alain Schnapp in the 17th lecture devoted to the memory of K. Th. Dimaras. But what is the relation between memory and ancient ruins, and how far do different civilizations converge in their appreciation of the material remains of their ancestors? From ancient Egypt to China through Mesopotomia and ancient Greece, Alain Schnapp explores the different ways that material remains relate to collective memory. Monuments imply their own future: their presence is a site of contestation and debate as one generation succeeds the other. The quest for the past uncovers the call of ancient civilisations to survive in time through memory. The fragile poetics of ruins address eternity. The comparative history of ruins suggested by Alain Schnapp evolves into a phenomenological endeavour: Past societies live their traces in space and construct an ecumenical and perpetually renewed cultural topos. Men of faith, men of political authority and men of knowledge, as well as standard and conventional mnemonic practices of everyday life contribute in conserving for posterity the symbolic capital necessary to any civilisation for its continuity.