Hereford Cathedral in the context of "Mappa mundi"

A T and O map or O–T or T–O map (orbis terrarum, orb or circle of the lands; with the letter T inside an O), also known as an Isidoran map, is a type of early world map that represents the Afro-Eurasian landmass as a circle (= O) divided into three parts by a T-shaped combination of the Mediterranean sea, the river Tanais (Don) and the Nile. The origins of this diagram are contested, with some scholars hypothesizing an origin in Roman or late antiquity, while others consider it to have originated in 7th or early-8th century Spain.

The earliest surviving example of a T-O map is found in a late-7th or early-8th century copy of Isidore of Seville's (c. 560–636) De natura rerum, which alongside his Etymologiae (c. 625) are two of the most common texts to be accompanied by such a diagram in the Middle Ages. A later manuscript added the names of Noah's sons (Sem, Iafeth and Cham) for each of the three continents (see Biblical terminology for race). A later variation with more detail is the Beatus map drawn by Beatus of Liébana, an 8th-century Spanish monk, in the prologue to his Commentary on the Apocalypse.

The Hereford Mappa Mundi (Latin: mappa mundi, map of the world) is the largest medieval map still known to exist, depicting the known world. It is a religious rather than literal depiction, featuring heaven, hell and the path to salvation. Dating from c. 1300 AD, the map is drawn in a form deriving from the T and O pattern. It is displayed at Hereford Cathedral in Hereford, England. The map was created as an intricate work of art rather than as a navigational tool. Sources for the information presented on the map include the Alexander tradition, medieval bestiaries and legends of monstrous races, as well as the Bible.

Although the evidence is circumstantial, recent work links the map with the promotion of the cult of Thomas de Cantilupe. Others link the map to a justification of the expulsion of Jewry from England. Potentially antisemitic images include a horned Moses and a depiction of Jews worshipping the Golden Calf in the form of a Saracen devil. The map may also reflect very patriarchal views of women as inherently sinful, including figures such as the wife of Lot being turned into a pillar of salt for gazing at the city of Sodom. Cantilupe was known for his dislike of Jews; in historian Debra Strickland's opinion he was regarded as misogynistic even by the standards of his own time.

Æthelberht (Old English: Æðelbrihte, Æþelberhte), also called Saint Ethelbert the King (c. 774 – 20 May 794) was an 8th-century saint and a king of East Anglia, the Anglo-Saxon kingdom which today includes the English counties of Norfolk and Suffolk. Little is known of his reign, which may have begun in 779, according to later sources, and very few of the coins he issued have been discovered. It is known from the Anglo-Saxon Chronicle that he was killed on the orders of Offa of Mercia in 794.

Æthelberht was locally canonised and became the focus of cults in East Anglia and at Hereford, where the shrine of the saintly king once existed. In the absence of known historical facts, medieval chroniclers provided their own details for his ancestry, life as king, and death at the hands of Offa. His feast day is 20 May. There are churches in Norfolk, Suffolk, and western England dedicated to him and he is a joint patron of Hereford Cathedral.