Issued in 1956, this Austrian commemorative highlights the XXIII International Congress for Housing and Town Planning, held in Vienna from 22–28 July 1956. The design by Seger features a pale green world map overlaid with red schematic urban layouts, symbolizing global collaboration in modern urban planning. The 1.45 schilling denomination reflects Austria’s mid-1950s postal rates for international mail. A clean, modernist layout and trilingual inscriptions (English, French, German) give it strong thematic appeal for collectors of architectural history, urban development, and international congress issues.