A new methodology is presented that measures density in urban systems. By combining highly detailed height measurements with, amongst others, topographical data we are able to quantify urban volume. This new approach is demonstrated in two separate case studies that relate to the temporal and spatial dimension of the urban environment, respectively. 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 spatiotemporal development of Amsterdam the self-organising-map approach is applied. Special attention is given to highlighting any signs of recent polynuclear development. The second case study compares the building-height frequency and spatial distribution of high-density zones in the four major Dutch cities. Additionally, the presence of built-up areas and the actual urban-volume values are explained simultaneously using a Heckman selection model.