The Poznań postcards presented by the University Library in Poznań form a collection that is the richest source of knowledge about the appearance of the city at the turn of the 19th and 20th centuries. The presentation of the Poznań postcards on the Mirabilium Collectio platform starts with postcards published between 1897 and 1910 by Carl Friedrich Wilhelm Nölte, and also includes postcards depicting Poznań fortifications.