The Cairo skyline is a maze of satellite dishes, rebar, minarets and pigeon lofts. Many of its rooftops hold informal housing, often for underprivileged immigrants from the countryside.

One rooftop stands out: the apartment of 78-year-old Shahira Mehrez, which tops a six-story building in the upmarket neighborhood of al-Dokki on the west bank of the Nile. Built in 1971 by renowned Egyptian architect Hassan Fathy, who pioneered the use of ecological materials and traditional building design in contemporary settings, the penthouse has been Mehrez’s home for the past 52 years. 

Mehrez is a designer, scholar and collector of traditional Egyptian costumes. With her French education and roots as a Muslim in Egypt, Mehrez always felt hinged between two worlds. “For the Egyptians, I was Fr...