Hi,
I don't think ill be any help with Norse, but I can offer some starting points for Greek based essays!
History of medicine is really interesting but 100 years might not be enough you could focus on:
-Who had more influence on the understanding of medicine Galen or Aristotle?
-What caused Greek ideas of medicine to spread? Why were Greek ideas so popular?
others topics about Greek history which I find interesting and easy to write about:
-Early Greek colonisation (why, where, who, patterns)
-Emergence of polis (theres a debate about why they emerged)
-If you're into warfare, the hoplite revolution might be interesting, how this played a role in the development of the polis
- Socrates vs Euthyphro on their ideas about religion and piety
- Persian and Peloponnesian wars
-Solon's reforms
-Why did Macedonian empire not survive after AtG
-Athens as the birthplace of democracy: can we say this is true?
-When did Greece become Greece? (Ideas about polis and unity)
If you want to talk specifically about a place, go for Athens! Lots of primary sources survive, makes your life easier.
This might have been useless, but hopefully this gives a few ideas of smaller timeline topics