The city of Rome is the archetype of the urban palimpsest, layer upon layer of history visible in a built fabric that documents a human presence from Etruscan times to the present day. Contrasting the changing forms of buildings and their functions, the network of streets and aqueducts, and the River Tiber provides instead a surprisingly stable armature of infrastructure that has received significantly less scholarly attention than the grand buildings of popes or emperors.Pamela O. Long’s book Engineering the Eternal City: Infrastructure, Topography, and the Culture of Knowledge in Late Sixteenth-Century Rome addresses a discrete part of the story of Rome’s complex infrastructure by considering a thirty-year period in the latter sixteenth century, spanning four pontificates from Pope Pius IV (r. 1559–1565) to Sixtus V (r. 1585–1590). As Manfredo Tafuri and others have shown, two primary forces shaped policies towards Rome’s urban fabric during this period, and indeed much of the modern era: on the one hand the need to resist through maintenance the entropic tendency toward decline of existing facilities, and on the other successive popes’ desire for memorialization through grand-scale urban interventions associated to their names. The prodigious efforts and significant investment documented for the period under observation show these two factors to be central to the provision and maintenance of infrastructure.