Normally, it is divided at the Suez Canal into Eurasia and Africa, the former of which can be subdivided into Europe and Asia. It can be divided alternatively into Eurasia-North Africa and Subsahara for cultural and historical reasons.
The mainland of Afro-Eurasia (excluding islands such as the British Isles, Japan,Madagascar and the Malay Archipelago) has been referred to as the World Island. (The term may have been coined by Sir Halford John Mackinder in The Geographical Pivot of History.)
Geographically, Europe is the westernmost peninsula of the continent of Eurasia; its limits are well defined by sea to the North, South and West. The Ural mountains are usually taken as the eastern limit of Europe, along with the Ural River, and the Caspian Sea. Europe can be considered bounded to the southeast by the Caucasus Mountains, the Black Sea and the waterways connecting the Black Sea to the Mediterranean. Europe's eastern and southeastern extent are discussed below.
Medieval Europeans considered Asia as a continent – a distinct landmass. The European concept of the three continents in the Old World goes back to Classical Antiquity, but during the Middle Ages was notably due to Isidore of Sevilla (see T and O map). The demarcation between Asia and Africa (to the southwest) is the Isthmus of Suez and the Red Sea. The boundary between Asia and Europe is conventionally considered to run through the Dardanelles, the Sea of Marmara, the Bosporus, the Black Sea, the Caucasus Mountains, the Caspian Sea, the Ural River to its source, and the Ural Mountains to the Kara Sea near Kara, Russia. While this interpretation of tripartite continents (i.e., of Asia, Europe, and Africa) remains common in modernity, discovery of the extent of Africa and Asia have made this definition somewhat anachronistic. This is especially true in the case of Asia, which would have several regions that would be considered distinct landmasses if these criteria were used (for example, Southern Asia and Eastern Asia).
Africa is the largest of the three great southward projections from the main mass of the Earth's exposed surface. Separated from Europe by the Mediterranean Sea, it is joined to Asia at its northeast extremity by the Isthmus of Suez (transected by the Suez Canal), 163 km (101 miles) wide. (Geopolitically, Egypt's Sinai Peninsula east of the Suez Canal is often considered part of Africa, as well. ) From the most northerly point, Ras ben Sakka in Tunisia (37°21' N), to the most southerly point, Cape Agulhas in South Africa (34°51'15" S), is a distance of approximately 8,000 km (5,000 miles); from Cape Verde, 17°33'22" W, the westernmost point, to Ras Hafun in Somalia, 51°27'52" E, the most easterly projection, is a distance of approximately 7,400 km (4,600 miles).
Although the interiors of Asia and Africa were not well known to Europeans at the time, their existence was known. Oceania and Antarctica are neither definitively Old World nor New World, since the terms "Old World" and "New World" predate their discovery by Europeans.