The Theatrum is widely recognised as the first modern atlas, which came to shape the future of cartography. "Shape and contents set the standards for later atlases, when the centre of the map-trade moved from Antwerp to Amsterdam. The characteristic feature of the Theatrum is, that it consists of two elements, forming part of a unitary whole: text and maps. This concept for a 'Theatre of the world' was followed through the 17th century. Before Ortelius no one had done this" (Koeman). The appended Catalogus Auctorum is a unique source of names of contemporary cartographers, some of whom would otherwise have remained obscure.

The three parts comprise: Theatrum, engraved title within architectural border, engraved portrait of Ortelius, Catalogus Auctorum with 153 names, 108 double-page mapsheets; Parergon, printed title within woodblock architectural border, 26 mapsheets; Nomenclator Ptolemaicus, printed title and woodcut device, dated 1591.