A skyline is a unique fingerprint of a city. The mentalities, diversity, and cultures in a city can often be perceived from its skyline. Istanbul's iconic skyline forms an essential part of the character and appearance of this mega city, so much so that Istanbul's historical silhouette is instantly recognizable; it is a unique asset that is important to protect. Impressive minarets and domes dominate the skyline of Istanbul. On the other hand, Istanbul's skyline has changed dramatically over the last decade since land has become increasingly an opportunity for investment and building of taller structures has become one way to multiply this profit. For those who focus on the esthetics of cities, the analysis of the skyline is not a recent phenomenon. However, skyline extraction and analysis has not usually been available in current GIS functionality. This article investigates the esthetics the urban skyline and its transformation due to high-rise buildings. It does this by tailoring a geomodel within a GIS environment. It is believed that the geomodel developed in this study will form a solid foundation which can be applied to many of the urban skylines and urban areas in Turkey and other cities of the world. (C) 2011 Elsevier B.V. All rights reserved.