For almost 2,000 years, the site of the battle was unidentified. The main clue to its location was an allusion to the saltus Teutoburgiensis in section i.60-62 of Tacitus' Annals, an area not far from the land between the upper reaches of the Lippe and Ems rivers in central Westphalia. During the 19th century, theories as to the site abounded, and the followers of one theory successfully argued for a long wooded ridge called the Osning, near Bielefeld. This was then renamed the Teutoburg Forest.