Rather than just one talk, I have a few options which are based on the Ancient world of Archaic, Ancient and Classical Greece. This is a subject that has fascinated me for decades and formed the basis of my early life and education. I have, essentially, three talks which can be adapted to suit your requirements.

1. The siege of Troy - the story of Paris, Helen, Achilles, Odysseus and many others. The talk uses the stories of the Iliad and the Odyssey as it's core but can be developed to discuss the mythology of the Ancients or the meanings that can be derived from the Trojan War or how it fits into the development of the Ancient world.
2. The Persian Wars - the core is about why they were fought, but the talk can be developed to focus on the key events such as Marathon, Thermopylae, Salamis etc or how they underpinned the development of the Greek world and - eventually - modern civilisation including the arts.
3. The development of Democracy - a tour around ancient Athens and how we can still see the world that they lived in and how they developed the early forms of democratic processes. The core is the early development of Democracy but can be modified to include the wars with Sparta, the growth of Athens and Greek culture and its rise to the superpower of the region.
4. With all of this material, I can also merge it into a 45 minute overview of the times to give your audience a flavour of what can be found for further reading or research.