Do not quote me on this, but I think that classical architecture is defined as architecture specifically from Europe and the Caucases. The time period dates from the time of Greek unification (600BCE) to somewhere around the middle ages. Ancient architecture would be considered Non-European architecture from the dawn of civilization. This would include ancient Egyptian architecture, pre-600 BCE Greek architecture, ancient Sumerian architecture, ancient Asian architecture, and everything else pre-600 BCE. I hope this helps.