The compass rose
As at the time (from the 13th to the 16th century), it was not yet the norm to position the north at the top of the maps, one or more wind roses were inserted there.
Some ancient seacharts (portulans) were very richly ornamented, dedicated to a prince or an admiral. They were of course not made for use at sea.
And in the richest manuscripts, compass roses can be particularly intricate with geometric, mechanical, and floral designs that, set in jewelry, look a lot like Art Nouveau.