Complex sentence: Limbo includes green fields and a castle with seven gates, to represent the seven virtues; itself the dwelling place of the wisest men of antiquity, including Virgil himself, and the Persian polymath Avicenna.
Split into simpler sentences: Limbo includes green fields and a castle with seven gates to represent the seven virtues. The castle is the dwelling place of the wisest men of antiquity, including Virgil himself, as well as the Persian polymath Avicenna.