River Malvam

The River Malvam (Anglicized: Malve), also known as the Malva was a mythical river in ancient North Africa where the Roman province of Mauretania would be. Mentioned by the medieval mytho-historians Geoffrey of Monmouth and Nennius in their histories, they say Brutus of Troy stopped there because his ships had run out of supplies. Geoffrey adds that his army conquered all the Mauretanian coast to resupply. After this restocking, the ships set sail for the straits of Gibraltar.

There is no need to consider the river anything more than a myth; the fact that is was repeated was probably because so much was plagiarized by medieval writers anyway.