The maps highlight the median age of buildings and the size of buildings and parcels. Information is distilled into 200-by-200-meter squares and color coded. The atlas gives each grid square a Character Score, which is a function of its buildings’ sizes and ages. This score can be compared to other measurable quantities, such as economic growth, to better understand the impact of older buildings within the city fabric. Other layers in the maps include National Historic Landmarks, City Landmarks, and National Historic Districts.