The Aegean Sea lies to the east of the Balkan Peninsula. A peninsula is a piece of land surrounded by water on three sides. The Balkan Peninsula is surrounded by the Mediterranean Sea, the Sea of Crete, and the Aegean Sea. The Aegean Sea borders Greece and Turkey.
The Balkan Peninsula is made up of several countries. Some of these countries include Greece, Albania, and Montenegro. The Balkan countries have played an important role in world history. During World War I, the empire of Austria-Hungary ruled many of the countries that now exist on this peninsula. The assassination of Franz Ferdinand, the heir to the throne of Austria-Hungary, led to Austria-Hungary declaring war on Serbia. This led to a series of events that started World War I.
To directly answer your question, the Aegean Sea is east of the Balkan Peninsula.