Two extremely rare and previously unknown engravings have been studied for the first time by VISU director Pieter Martens. Both prints survive in a single impression only and were unpublished until now. The first, preserved at the British Museum, has been identified by Martens as a depiction of the siege in 1536 of Appingedam (Damme), a small town in the Northern Netherlands between Groningen and Delfzijl. Its discovery is published in Caert Thresoor, the only Dutch journal devoted to the history of cartography. The second print, preserved in Wolfegg, is a hitherto unknown etching by the famous Antwerp printmaker Hieronymus Cock depicting the Spanish siege in 1558 of Centallo, a small town in Piedmont, Italy. This important find is published in Print Quarterly, the leading international journal dedicated to the history and art of the print. Both engravings also constitute precious historical records as they both are the only known visual representation of the events they depict. Their discoveries shed new light on the early development urban cartography and printmaking in the Low Countries.