Ibn Tulun Mosque is the oldest mosque in Egypt and one of the oldest in the world (approx 1200 years old), most notable for its minaret based on the famous one at Saqqara. It's eerily deserted, something I did not expect, and is off the beaten track for tourists (though I went in July) - a must see.
A visit to the Monastery is a must. While a bit of a trek (set off early morning to avoid the heat of day), the route can be walked, or you can be taken up by Donkey.
Either way, it's well worth it, with a cave cafe opposite the Monastery to relax, take in the atmosphere and recharge your batteries
Send your feedback or queries to email@example.com