After a period of exorbitant growth in building sector, it is appropriate to measure the impact it has had on the spatial structure of the main Spanish metropolitan areas. Madrid, Barcelona, Valencia, Sevilla, Bilbao and Zaragoza are surveyed, and two periods are compared: 2001 and 2011. The main driving factor behind the evolution of urban density is the huge and fast arrival and settlement of immigrants. This article explores these transformations through exploratory spatial data analysis and classic econometric models that relate urban density with distance to central business district. The presence of spatial effects is tested: spatial lag and error models are considered. Spatial error models are estimated. Two main consequences of real state bubble are as follows: (1) spatial autocorrelation has grown and (2) in Madrid, Barcelona and Zaragoza central areas with high urban density are larger than before. From a methodological point of view, the introduction of spatial effects in the classical urban population density models implies a clear reduction in the explaining power of distance.