Lets define greatest as: Influence over other nations(Not just conqured ones), Land, Philisophy, Scientific advances, Military, and Leaders. Also what stage where they at compared to the rest of the world at that time?
General Rules, Like watch your language, you get it.
NOTE: Preferably when they were as good as they ever got.
Greece. Democracy originated from Greece. Philisophy as well. They housed the noble spartans who fought to the death to give the other men time to get away, to fight another day; in the Battle of Thermopylae. Greece greatly influenced the great Romans. The Greeks influenced the Western World more than any other civilization in my opinion. Who could forget Alexander The Great, he conqured practicaly the known world. Compared to other civilizations at that time Greece was highly advanced in science and they were very capable of defending their land as well as gaining more land. The Romans only conqured them due to Alexanders death, when Greece was split into three seperate countries.
Let the debate begin.