I imagine the first thing that most people think of when they hear or read that is Athens and Sparta. Similarly, Ancient Rome easily evokes a whole host of well-known images and characters (Scipio Africanus, Julius Caesar, Caligula etc).
If you mention the Middle Ages, people will think of the Black Prince, Henry V, Agincourt, knights and, perhaps above all else, English longbows.
But there’s a thousand years or more between the pomp and glory of Rome’s power and the premature death of Edward of Woodstock. Hastings and Vikings fill a bit of the gap, but the rest of it seems to be almost a black hole of history.
The Byzantine Empire is the obvious superpower that fills the gap, yet it’s remarkably unknown. I’m not a historian, but I’d also not describe myself as historically ignorant, and I knew sod all about Byzantium until quite recently.
It lasted for over a thousand years and mingled Greek mysticism with Roman power, and acted as a long term bulwark for Europe against the Persians and, latterly, the Ottoman Empire.
In acts that now read as little more than insanity, the Catholic Christians of the West organised a Crusade against Greek Orthodox Byzantium, leading to a period of exile for the rulers (though they did regain the city in time). Byzantium was, by turns, assisted, despised and ignored as the Emperor desperately sought aid to see off the Ottomans.
Sadly, this didn’t happen. Byzantium fell in the most tragic circumstances possible and the city’s unique position within the world of culture and religion was lost. Now, Byzantium/Constantinople is better known as Istanbul.
The history is as fascinating as the Roman period (although more topsy-turvy, as Byzantium’s power waxed and waned regularly whereas the Rome’s power expanded for ages and then slowly collapsed), and it’s baffling as to why it isn’t better known.
Maybe it’s because Byzantium never ruled over Britain (it sort of overlapped a bit with the unified empire but when the West/East split happened Blighty was always Western) and was rather further away than Rome. Plus, the destruction of Byzantium as a religious rival to Rome will have decreased its spiritual status. (There are still many churches in Istanbul, but the city itself is mostly Muslim, obviously).
It might also be because the writers of history might have been reluctant to dwell on the fact that the Christian West alternated between ignoring Byzantine pleas for help and actively harming the city state as it tried to defend itself from the expanding Ottoman Empire.