The Palazzo dei Priori in Perugia, Italy, was built between 1293 and 1443 . Those who have visited this city will recognize it immediately at the outside.
Inside it is full of art works and one can stroll in admiration for several hours. In the Portale Maggiori, finished 1346, don’t pass (as I did) without noticing this snail… .
 Image through courtesy of Clemens Brandstetter.