Teams were sent to nearby Gerke Alley to find and take a picture
of a flyer:
Flyer
Alert puzzlers might notice that the countries' initials form the
word VISITS; that's not relevant to the puzzle; it was part of the
game-day hint system.
Then they returned to Washington Square Park, showed GC their flyer-picture, and received a crossword puzzle:
In addition to the usual answer-checking, this box will also respond to
"answers" like 45A or 49D
with the answers to 45 Across or 49 Down.
(On game day, teams chose six free crossword answers.)