Ammianus Marcellinus (30.3
) mentions a fortress named Robur, which Valentinian I., A.D. 374, built near Basilia (Basle
) on the Rhine in Switzerland. Schoepflin guessed that Robur was on the site of the cathedral of Basle,
but the words of Ammianus do not give much support to this conjecture: “Prope Basiliam, quod appellant accolae Robur.” Others have made other guesses.