I know an architect who asked about interesting places for him to visit in Cairo, any suggestions?

Answer 1

New or old?

Old there's plenty a-bounding from Ancient Egyptian to Roman to Islamic.

Old Cairo is a good place to see Roman-Coptic architecture such as the Hanging Church.

Islamic Cairo is a medieval treasure trove of old mosque, the citadel, marketplaces, cemetaries and an aqueduct.

For Ancient Egypt, they'll have to go to Giza to see the pyramids.

Modern architecture can be found in newer areas like Zamelek, El Maadi and Doqqi (I think that's how you spell it).

Some newer buildings of note: Cairo Tower in Zamelek, Cairo University in Giza, Egyptian Musuem, there's a 19th century (?) Baron's house in Heliopolis that is really bizarre.

check out Wiki for more suggestions:
http://en.wikipedia.org/wiki/Cairo