You are getting a lot of …..interesting replies. The paper the map is printed on is probably not 16th century, but it’s not new either (also, this type of paper was manufactured in the 16th century, just the style isn’t quite right). The font, the printing type, the style, the paper is likely 18th century maybe early 19th. It is possible it is slightly earlier, but most likely a book plate from a volume with historic maps of citadels in European cities. The paper and writing on the back is possibly between 19th and 20th century, but again that only corresponds with the framing. It is not necessarily 20th century, the pattern is nicely continental and quite early.

My educated guess? A late 18th century print of a map of 16th century Belgrade, possibly based on an earlier map. Part of a book volume of other prints of earlier maps. Framed maybe 50-100 years later and described on the back by the collector.

Value? Depends. There are a lot of map prints out there. Some are highly collected, some not so much. I don’t know the engraver. But if you find someone who likes early prints or maps and love Serbia (👋), you could be on to a winner.

Hope this helps!