To be honest this is my homework question. I don't have the textbook just yet so I was wondering if someone could just point me to a good resource to read up on this.

EDIT: I am pretty sure it has to do with their Pyramids structures and Hieroglyphics writing. The writing gives them immortality but I think the question is asking how did it last. Possibly the geography helped maintain the empire? I also think mainly due to their technological advances.

Geography - Egypt is highly defined and defensible geographically. Assyria is open to invasion and migration from practically every direction.