Bavaria is a country that is very rich in prehistoric fortifications. In our early histories the construction of these is attributed almost without exception to the Romans; it is only the more intensive study of genuine Roman work that has enabled us to distinguish between pre-Roman, Roman and post-Roman remains. Moreover other fortifications, which are today invisible, have been re-discovered by a systematic investigation of the ground. These fortifications were evidently not constructed regularly throughout the prehistoric era but appear at intervals in large numbers, from which we can readily trace their erection to political causes. Two main types can be distinguished at once: circular camps that are built on a hilltop or plateau, and promontory camps, built to protect the landward approaches of a mountain spur or of a spit of land bounded on its other sides by valleys or river-beds. We also find one other type, the rectangular, which was unknown until the late La Tène period and survived for only a short time.