only away from a relatively straight line between Mannheim and Basel, it is also higher than any other city on the Rhine Valley Railway north of Haltingen and in particular it was 308 Baden feet or 92.4 metres higher than Kenzingen, which is located 25 kilometres to the north. Alternative routes through the Rhine Valley that omitted Freiburg, running either from Riegel to Hartheim or from Kenzingen to Biengen near Bad Krozingen, would have been much shorter and would not have involved the gradients required to climb to the Freiburger Bucht (the lowlands around Freiburg) at the foot of the Black Forest. The commission's proposal for the construction of the line to begin in Mannheim, Freiburg and Isteiner Klotz (a hill south of Schliengen) had not come about. The commission wanted to wait to benefit from the experience of the construction of the line from Mannheim and found that this approach facilitated the work while also allowed a degree of flexibility in the operation of the line. According to the law of 1838 work should have started immediately, at least preliminary work, so "that the progress of the railway is stopped nowhere" (daß die Bahn in ihrem Fortschreiten nirgends aufgehalten wird). After a proposal to build a passenger station at a site in Lehen in the area of the current A 5 autobahn was excluded as being located too far from Freiburg, it decided to build the line immediately west of the city through the "Vauban belt", the flat zone previously kept clear for firing cannon-shot from the fortifications (Festungsrayon) designed by Sébastien Le Prestre de Vauban. There was plenty of space for an extensive network of tracks. This solution, however, required a grade of 1:171 (0.58%, according to other sources 0.53%), the largest grade on the Baden mainline. This required levelling of the route from Köndringen, continuing to the south to Schallstadt. The railway reached Offenburg on 1 June 1844 and construction began on the section from Riegel to Freiburg in 1841. In 1843, the cornerstone was laid for the station in Freiburg; this ceremony involved the transportation of the locomotive, Der Rhein of the Maschinenbau-Gesellschaft Karlsruhe ("Karlsruhe Engineering Works") over the highway to Freiburg. On 22 July 1845, the first trial train to Freiburg ran with six carriages, hauled by the locomotive, Der Kaiserstuhl of Baden class IIIc. Another trial followed on 26 July with the locomotive Keppler,