I would say an hour and a half. It's not that big inside. They'll have art exhibitions from locals, paintings, story about the real Parthenon in Greece and the main attraction, the huge statue of Athena. It's the tallest indoor statue in the U.S. and its covered in gold.
To walk around the outside of the building at a slow pace, I would say no more than 5 minutes. To walk around inside the museum on both floors, about 2 hours if you want to read some of the info and see everything. You can definitely just skim by stuff and shorten that, or lengthen if you want to read everything.
One hour inside the museum. Two hours outside in the park.
I would give yourself about 2 hours that should be enough time to take it all in.
I would agree with both. It's really up to you on how long you wish to spend looking in the museum. The building it's self is not that big.
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