The Breisgau, which in the Middle Ages also included the Markgräflerland and parts of the High Rhine, is today considered a region with a notably low number of castles, in contrast to the neighboring areas of Alsace and Northwestern Switzerland. However, as the already published volumes 1 and 2 of the project "The Castles in Medieval Breisgau" demonstrate, this assessment needs to be revised. With the third volume, the research team led by editors Prof. Dr. Alfons Zettler (Dortmund) and Prof. Dr. Thomas Zotz (Freiburg) now expands into the southern part of medieval Breisgau and has for the first time compiled a scientifically grounded inventory of all castle sites in that area.