I've been playing through Odyssey, which I believe takes place during the Peloponessian War. As I'm exploring the game there are a lot of places that are already "ruins" throughout the world, which seems crazy to me? Is that accurate? Was Greece already old enough by the 400s BCE to have ruins? How early did classical Greek society form? (and I'm using "classical" in a very laymen way, I'm sure it has a specific meaning to historians). Thanks!
There are palace ruins dating to 2000 BC in Greece, so in short, Greece was old enough. Just for comparison, by the Peloponnesian war in question, the Iliad would already be around 200 years old and (ruins of) Mycenean Greece 1000 years old. What we consider Classical period (not necessarily classic) in Greek culture, is merely one epoch which starts from mid 5th century BC (c.450) and lasts until c. 320's BC.
The date is a convention though. To put it into context, it wouldn't include all those nice, black figure vases everyone thinks of when Greek art is mentioned, it wouldn't include famous bronze clad warriors and their Corinthian helmets, and it wouldn't include famous Persian wars, and battles of Thermopylae or Plataea. They belonged to a so called Archaic period (c.750-450 BC) that preceded the Classical age. Term Classical, however, is sometimes confusingly used by non specialists to describe this entire period, or even antiquity as a whole.