The Beautiful Fountain Schoner Brunnen was completed in Nuremberg in 1396 and is possible candidate for the famous 'Tower in the hole' from the nine-rosette page of the Voynich Manuscript. Here is how the plaza in Nuremberg looks today.
UPDATE: Eleonore Menzel from the City of Nuremberg administration kindly explained that the square structure on the Hauptmarkt plaza is not related to the fountain - it just modern artwork.
Norbert Heinlein from the Hochbauamt Department in Nuremberg explained that years ago there was a bigger fountain in the same plaza - 20th century copy of the17th century - Neptunbrunnen, which was sold to Russia and was never installed in Nuremberg.
Illustration from 1707 shows fountain-like structure in the middle of the plaza, but it could be something else.
15th century Nuremberg was a big city for its time and we get some idea how it looked like from the Nuremberg Chronicles.