Free. Reservations are highly recommended. Children must at least be in the first grade to take the tour.
Visitor center open Mon.-Fri. 8:30-3:30 (also Thurs. 3:30-6). Tours depart at 9:30, 11:30 and 1:30 (also Thurs at 6); phone ahead to confirm schedule. Closed holidays and the third week in July. Allow 1 hour minimum.