In Roman times, as today, building projects unfolded in the real world, with real, physical constraints – and therefore, such projects at all times were always strongly conditioned by the shape, the texture, and the temperature of the world in which the builders lived and moved. In order to assess the ecological footprint of Roman construction, we thus need to ask how building works were organised to cope with environmental challenges, such as the limited local availability of resources, drops in temperature, or changing levels of rainfall. Seasonally fluctuating water levels made riverine transport difficult and often dangerous; in heavy rain, metalled roads became slippery and unpaved roads impassable; and, as Vitruvius reminds us, even the choice of building stones such as particular types of tufa were conditioned by the knowledge that some of them would not be as affected by exposure to the elements as others. The aim of this paper is to establish first parameters for modelling the ecological impact of Roman building projects. The paper will first focus on a reconstruction of the climatic conditions for Roman construction beyond the very limited textual evidence, before discussing one particular case study from the northwestern provinces in order to illustrate how Roman architectural practice was influenced by and, in return, profoundly shaped the environment.