The colosseum was a building that could be flooded, and nowadays we use the same idea with swimming pools.
The idea being the colosseum was that people could come and see shows; we have stadiums and theatres for that today.
Your deductible.
When you file a claim against your insurance the amount that you have to pay is the deductible. You will pay your deductible and then the insurance company pays the amount that is left to be paidl