Is there a time when admission is free or are there pay what you wishes days and hours. Phil

From the web (the same info we got when we asked at the information desk): Every Saturday, from 5–7:45 pm, you can pay what you wish for admission (cash only). Suggested admission is $10 and the last ticket is issued at 7:15 pm. Remember that City Pass has the option Top of the Rock or Guggenheim.

It is pay if you want take a tour any date at any hour