From lock 1 until shortly before lock 13 the old canal was following the river Altmühl. At places, where the river had to overcome larger difference in elevation weirs where built. The photograph was taken from the weir belonging to lock 12. At the left hand side of the picture we can see the branch of a short navigable canal. At the end of the canal lock 12 was built. Another possibility is, to integrate lock and weir into one building, as e.g. at lock 11.