This report surveys a successful attempt to build a HGIS (historical geographic information system) of liturgical processional routes in the city of Constantinople (modern day Istanbul) during the 9th and 10th centuries. Data about the routes was gathered from the Typikon of the Great Church, a medieval book describing the liturgical ceremonies of the Hagia Sophia, the largest and most important church in Constantinople during the Byzantine era. Information about the different churches mentioned in the Typikon was gathered from a variety of sources, most notably from Raymond Janin's multivolume series on the subject. Major problems during the construction of the HGIS were finding accurate information on churches that no longer exist, constructing a map of an area which is dramatically different today topologically and the lack of English language sources. Despite these problems, the resulting HGIS allows for a clearer view of how processional routes moved across the city.