Is it possible to buy tickets to visit the UN in advance (i.e., not day of)?  The website below seems to suggest that tickets are sold day of only ("sold on the day") -- just wanted to check here before waiting in line.  Thanks!

https://www.unog.ch/80256EE600581D0E/(httpPages)/5ADC7FB14E2750BD80256EF7005848A2?OpenDocument