For many its the Roman empire or the Greeks. Similarly ancient Egypt. Or the British empire. Maybe the Japanese, Chinese and Norse as the next 3.
I have deliberately not mentioned time periods there.
These are the most commonly beloved. What are your favourites and why?
WW2. It really was the greatest generation full of amazing and terrible people. Winston Churchill story alone is breathtaking let alone all the smaller stories and experience of all people who played a roll large or small.