In the Axial Age (mid-first millennium BC), a continuous belt of civilizations stretched through the Eurasian subtropical zone from the Atlantic to the Pacific. This belt became the mainstream of world history for two millennia. Originally, “Eurasia” is a geographical notion: in this sense, it is simply the biggest continent; the combined landmass of Europe and Asia. However, geopolitically, the word has several meanings, reflecting specific geopolitical interests. “Eurasia” is one of the most important geopolitical concepts and it figures prominently in the commentaries on the ideas of Halford Mackinder. As Zbigniew Brzezinski observed on Eurasia:  The Russian "Eurasianism" corresponded initially more or less to the land area of Imperial Russia in 1914, including parts of Eastern Europe. One of Russia's main geopolitical interests lies in ever closer integration with those countries that it considers part of “Eurasia.” This concept is further integrated with communist eschatology by author Alexander Dugin as the guiding principle of "self-sufficiency of a large space" during expansion. The term "Eurasia" gained geopolitical reputation as one of the three superstates in "1984", George Orwell's novel where constant surveillance and propaganda are strategic elements (introduced as reflexive antagonists) of the heterogeneous dispositif such metapolitical constructs use in order to control and exercise power. Across Eurasia, several single markets have emerged including the Eurasian Economic Space, European Single Market, ASEAN Economic Community and the Gulf Cooperation Council. There are also several international organizations and initiatives which seek to promote integration throughout Eurasia, including:     In ancient times, the Greeks classified Europe (derived from the mythological Phoenician princess Europa) and Asia (derived from Asia, a woman in Greek mythology) as separate "lands". Where to draw the dividing line between the two regions is still a matter of discussion. Especially whether the Kuma-Manych Depression or the Caucasus Mountains form the southeast boundary is disputed, since Mount Elbrus would be part of Europe in the latter case, making it (and not Mont Blanc) Europe's highest mountain. Most accepted is probably the boundary as defined by Philip Johan von Strahlenberg in the 18th century. He defined the dividing line along the Aegean Sea, Dardanelles, Sea of Marmara, Bosporus, Black Sea, Kuma–Manych Depression, Caspian Sea, Ural River, and Ural Mountains.