Answer:
The level of education and vast possession of knowledge. The scholars of Timbuktu were very learned that Kings at the time called them to settle disputes. A manuscript was recently found in Timbuktu. It was on algebra which was translated to French and taken to France for study. The result indicated that it would be a material that would be taught today in second level of University Education.
The people of Timbuktu were exceptionally educated even by today's standards. Though religious studies was a part of what they studied but they made sure to study everything they find.
Such a historic center of learning cannot be replaced.
