The document discusses four important centers of ancient education in India: 1. Nalanda University was a renowned Buddhist center of learning from the 5th to 12th century CE with entrance exams, renowned teachers and library. It declined after an invasion in 1193 CE. 2. Vikramashila University was also an important Buddhist center from 8th to 12th century CE that declined after the same 1193 CE invasion. 3. Taxila University was a famous center that attracted scholars from across India, especially in fields like medicine. 4. Kashi (Varanasi) was mentioned as an important center as early as the 6th century BCE and developed further as a center of philosophy after the epic period