Recent archaeological studies have described Sri Lanka’s great Mediaeval capitals, Anuradhapura and Polonnaruwa, as examples of “low-density urbanism”. In doing so, such literature draws comparisons between the form and layout of Anuradhapura and Polonnaruwa, and the urban landscapes of the Khmer in Cambodia, or of the Classic Lowland Maya in Mesoamerica. However, to date, no actual population density estimates have been produced for the urban landscape of either Anuradhapura or Polonnaruva. Moreover, unlike the vast urban sprawl of Angkor, the hinterland of Anuradhapura is characterised by settlement that might better be described as simply “rural” – with the population living in small, short-lived settlements that take little to no part in administration, industrial activity or long-distance trade. At Polonnaruwa pilot surveys appear to show a quite different settlement pattern, with larger hinterland settlements showing evidence of playing a far greater role in economic administration – but these still don’t necessarily appear to represent “low density urbanism” and might instead be described as something approaching “towns”. This paper reviews applications of the “low density urbanism” label to Sri Lanka’s great mediaeval capitals, examining population density estimates, urban form, and core-periphery interactions.