Answer:
<em>The Olympic flame, one of the most visible symbols of modern games, is a tradition of Ancient Greece.</em>
or
<em>The Olympic flame, a tradition of Ancient Greece, is one of the most visible symbols of modern games.</em>
Explanation:
An appositive refers to a noun or noun phrase, usually between commas, which defines, identifies or describes the noun it follows. As a result, both possible appositives between commas illustrate the noun <em>The Olympic flame. </em>Therefore, both establish it as either a symbol of the modern games or a tradition of Ancient Greece.