This point layer displays the Central Business District (CBD) of Ulaanbaatar, Mongolia as a point corresponding to the location of its city hall. For the compactness metrics, the proximity index measures the relative closeness of all locations in the city to its center. To calculate the proximity index, the Equal Area Circle was defined as a circle with an area equal to that of the urban footprint centered at the city's city hall within the CBD. This data is part of the Atlas of Urban Expansion. The Atlas of Urban Expansion provides the geographic and quantitative dimensions of urban expansion and its key attributes in cities the world over. The data and images are available for free downloading, for scholars, public officials, planners, those engaged in international development, and concerned citizens. The global empirical evidence presented here is critical for an intelligent discussion of plans and policies to manage urban expansion everywhere. This resource provides both the conceptual framework and, for the first time, the basic empirical data and quantitative dimensions of past, present, and future urban expansion in cities around the world that are necessary for making minimal preparations for the massive urban growth expected in the coming decades.