With it getting closer to summer and the weather warming up people will start to line up earlier every day. Tours are Mondays thru Thursdays. There are no slow days unless the weather in the morning is bad. People will start lining up for tickets as early as 5am. Tickets to get tickets (I know, its odd) are handed out early. Actual tickets are handed out at 7am. They go fast.
You need tickets (it's free). I went on a slow day and walked up right before the tour. If it's busy you may have to wait a bit
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