A new methodology is presented that describes the density of urban systems. By combining highly detailed height measurements with amongst others topographical data we are able to quantify the urban volume. This new approach is tested in two separate case-studies that respectively relate to the temporal and spatial dimension of the urban environment. In the first study the growth of the city of Amsterdam over the past century is studied. The urban volume indicator is used to visualise and quantify the urban extension and intensification process. To critically analyse the spatio-temporal development of Amsterdam the self-organizing map approach is applied. Special attention is given to highlighting any signs of recent polynuclear development. The second case-study compares the spatial distribution of high-density zones of the four major Dutch cities. ; publishersversion ; published