You can see rocky steps anytime as far as the art museum I wouldn't know but you can look up their sight and look for times
It used to open 24 hours, but since they installed a new gate, I'm not sure if it's the same hours anymore.
There are also some segway tours that depart from the bottom of the steps, however you would have to search to find out the name of the company doing the segway tours and what time they start.
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