Complex sentence: The velarium that covers the Colosseum in Rome had a use of giving off shade and slight protection from rain, although the main use of the Velarium was to create a ventilation shaft creating circulation and a cool breeze.
Split into simpler sentences: The velarium that covers the Colosseum in Rome had a use of giving off shade and slight protection from rain. Although, the main use of the Velarium was to create a ventalation shaft creating circulation and a cool breeze.