Walled Jews

When people hear about the walled Jewish quarters of the Middle Ages, the ghettos of more recent European history naturally come to mind. But, in fact, the walls were often desired by the Jews themselves. In fact, when a ruler or city government wanted to attract Jews, it was apparently not an unknown promotional technique to build a walled quarter of a city, and then invite Jews by boasting of the feature, "And look, you'll even have a wall!"

Source: Prof. Phillip Daileader, The High Middle Ages

By the way, the Teaching Company's courses on history are much more reliable than most pop history books: they are almost always taught by someone whose specialty is the period on which they are lecturing, and who thus has spent years studying the period, but even more importantly, years having their work on the period peer-reviewed at conferences and for journal submissions. Furthermore, these lecturers spent many years being trained as historical researchers. Now, this doesn't mean they never make mistakes, but it does mean they will rarely make the ridiculous mistakes to which pop history writers are prone. (It also doesn't mean every work of popular history is bad! Good journalists, in particular, largely have the right attitude and training for historical research; in particular, they know to interrogate, rather than to believe, their sources.)