Cleopatra VII fought to keep Egypt independent, bearing Julius Caesar a son, and then allying herself with Mark Anthony.
They therefore guarded the important trade routes, and in 130 AD Emperor Trajan rebuilt the fortress of Babylon-on-the-Nile.
Alexandria was effectively left alone, and remained the cultural and administrative capital of Egypt.
Cairo is a city in which the past and present are inextricably intertwined. Despite the presence of the Pyramids, Cairo is not technically a Pharaonic city.
Rather, it is an amalgamation of separate cities that were established by successive conquerors since Persian times.