More on the cities of refuge -- what kinds of cities are suitable for this purpose? Medium-sized cities, with water available, and marketplaces, and a sizable enough population -- which should be replenished if those numbers drop. Also, if a student (of Torah, presumably) is exiled, his teacher is exiled with him -- as essential to his life. Which points to the idea that people should only teach suitable students (who are not likely to end up in a city of refuge). If a teacher is exiled, the entire yeshivah goes with him too. Plus, the sages and the verses they used to learn out details about those who kill inadvertently. In the hopes that all happens as it should. Also, a city of refuge that is already home to a majority of unintentional killers cannot accept new ones. Plus, what happens in a city that has no elders to begin with?