Frequently Asked Question: I'm on Memory Block 4 and there's nothing left to do on my map. What now?
Answer: Go to the Bureau and listen to the Rafiq. He will give you hints on which direction to go. A new District in the city is now accessible to you (no more blue memory wall). It's still blurry on your map with no icons.
Go to this new district and get on a roof. Scan the horizon for high points with eagles circling them. These are new View Points. Climb one and synchronize. Now check your map again.
This video tutorial demonstrates the process in Damascus, where you will assassinate Abu'l Nuqoud.