“Ruins: Temporality and Transformation” examines the ways in which the ruins and derelict structures that are an important component in many of Ruisdael’s landscape paintings suggest a key role of the man-made within the natural world. It examines just how ruins in landscapes convey a sense of temporality, which I call “biological time.” That is, each living thing follows its own course in time; a concept that appears in contemporaneous medical literature. This chapter analyzes the way ruinous buildings are set off by elements—vegetation, rushing water, clouded skies, and light effects—that make manifest different stages of transience and endurance. Ruisdael’s views of Amsterdam from its scruffy outskirts provide another perspective on this theme.