Tagus

The Tagus is the longest river of the Iberian Peninsula, flowing westwards through central Spain past Toledo and reaching the Atlantic at Lisbon. In the medieval period it formed an approximate frontier zone between Christian kingdoms and Muslim al-Andalus. Accounts of the Almohad Caliphate use it to mark the northern limit of an empire that at its height stretched from the Atlantic to Tunisia and from the Sahara to the Tagus.