Ibn Tulun Mosque is both the oldest and the largest mosque in Cairo. In view of its architectural and social importance, its restoration proceeded according to the principle of minimal intervention, respecting the original fabric while erasing the damage caused by previous works (for example, by removing the earlier cement mortars that had given rise to cracks). More than 350 people were involved in the project. Working with foreign experts, they had the opportunity to gain experience in a broad range of techniques, in the process significantly advancing the skill base for conservation in Egypt.
Source: Aga Khan Trust for Culture