Drama in Western culture has its roots in the theater of ancient Greece. The playwrights of fifth century Athens created dramatic structure. Its philosophers and rhetoricians, principally Aristotle in the Poetics, defined the theories of tragedy and comedy, concepts that hold true to the present day. Its architects created amphitheaters. The Romans, admirers of Greek culture, continued the theatrical tradition by writing and performing plays in their own amphitheaters. The remains of their amphitheaters as well as their viaducts survive to this day across Europe and the Mediterranean in what were once Roman colonial outposts.