According to Jewish sources, Shem (son of Noah) and his great-grandson Ever ran a yeshiva (house of Jewish study). There is a tradition that this unimpressive-looking cave in Safed was the site of their yeshiva. How did this cave come to be identified as such? The Torah is divided into two parts - hidden and revealed - and one might assume they were not studying the revealed Torah, since Moses had not yet been born. So they must have been studying the hidden Torah. And where better to do that than in Safed?