Find location #2!
You solved puzzle 1, well done! The smaller building in front of the Volkenkunde Museum was built in the 19th century as the Boerhaave Laboratory, part of the larger Academic Hospital complex that now houses the museum. During WWII part of the laboratory was destroyed by a badly aimed bomb.
As a reward for solving the puzzle, you get a symbol for the end solution – remember it well!
And here is a photo clue for the next location of the treasure hunt, puzzle #2: