What advanced civilizations existed around the time of the first crusade?

Around the time of the First Crusade (1096-1099), several advanced civilizations thrived. The Byzantine Empire, with its capital in Constantinople, was a major center of culture and learning, preserving ancient Greek and Roman knowledge. In the Islamic world, the Seljuk Empire was prominent, and cities like Baghdad were hubs of science, philosophy, and trade. Additionally, the Fatimid Caliphate in North Africa and parts of the Levant was influential, known for its architectural advancements and vibrant cultural life.