If we acknowledge that Central Europe exists, there is no agreement as to its whereabouts. What about its center? Would Berlin, Prague, or Vienna be its center? Are the Balkan states part of Central Europe? What about Poland? And who actually are the Central European? The answer changes from country to country, too. The Hungarians, like the Czechs, tend to consider the old Austro- Hungarian Empire to be the historical core of Central Europe, which they often prefer to call the ``Danubian Domain.`` For the Poles, Central Europe covers the whole area between Germany and Russia. In conclusion, there are no precise or uncontestable answers about where Central Europe starts precisely, and where it ends. The main thrust of this paper is to search answers about where Central Europe is. In order to do that, I will define the concept of Central Europe from the perspective of the relationship between European community and Central Europe. European community`s centuries-long confrontation with the Ottoman Turks helped define Central Europe as a cultural and historical region. Especially in the 16th century, Central Europe played a key role as a bulwark of Christendom against the Turkish menace. Several criteria are used to define Central Europe as a region distinct from Western, Eastern and the Balkan Europe. One of them is the bulwark metaphor. The term, "a Bulwark of Christendom," is used to describe Central Europe as a regional concept. The bulwark of the medieval Christian world against the Ottoman Turks was Hungary. From 1390, the first year the Turks invaded the Hungarian frontier, Hungarian kings had to devote attention to the Turkish menace on the Danubian frontier. But, Hungary was defeated by the Ottoman Empire at Mohacs in 1526. After that, Hungary could not play the role as a bulwark against the Turks. If the defeat was a national tragedy for Hungarians, Austrians simultaneously saw it as a good fortune in their history because it was the birth of the Habsburg`s Central European Empire. From the Austrian perspective, when Ferdinand Ⅰ assumed the Hungarian crown, the Habsburgs also shouldered the responsibility for defending Christendom. Accordingly, Ferdinand Ⅰ decided to shield the Central European nations including Austria, Bohemia, Hungary, and the Holy Roman Empire against the Turks. In order to do that, he had to establish strategic partnership with one another, standing up against the Turkish menace. And then, he drew up a new defense network throughout Central Europe. In 1558, after he was crowned to the Roman Emperor, the Habsburg`s Central European Empire came to a bulwark of Christendom against the Ottoman Empire. After all, the confrontation between the Christian West and the Islam East consolidated a bulwark as metaphor that Central Europe used to define its role in European history as well as its relationship with European community.