This map appears on page 360 of Isidore of Seville’s Etymologies (available through the Library of Congress under a longer title (Isidori Iunioris Hispalensis Episcopi Liber etimologiarum ad Braulionem Cesar Augustanum Episcopum scriptus incipit foeliciter).
Isidore of Seville (560—636 CE)
The author of the widely circulated manuscript in which the first known map of the world appeared in this shape.
The Dniper river in the north and the Nile River in the south often were the basis for the two sides of the “T” in the T-O map.
View T-O map in a larger map