Newbie here, just fascinated with the sleuthing end.
After checking many tourist ideas, seems that one of the really interesting things besides Wulff Castle is Fonck Museum of Archeology and Natural History. They can see the Easter Island Muai, the only Muai on South America's mainland. Since it's full of fossils and one of a kind relics (two headed goat was mentioned by one traveler), I could see them having the racers look for something titled in Spanish, where they will then get their next clue. Also, I believe the museum is closed on Mondays, so production may have planned it that way to eliminate other interference? Do they do that?
I hope this is OK to post here. I am not wishing them to go here, just seems plausible with the seemingly limited amount of task things to do here.