Yes it is free. You need reservations...online...I found it easy to get 6...open 2 Saturdays per month.
It is, but you must have a reservation or be accompanied by an Amazon employee. The reservations are only open 2 weekends a month and they go pretty quick. Those escorted by an employee can go any time during open hours. However, to get an employee escort you need to have a friend or relative who's an employee - they don't take kindly to random people asking them to provide an escort through the spheres.
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