According to Official Guinness Records,
The largest panoramic postcard covers an area of 86.40 m² (930 ft²) and was achieved by Magyar Reumabetegek Egyesülete (Hungary) at Millenáris Park in Budapest, Hungary, on 12 October 2013.
The postcard was created by the Association of Hungarian Rheumatoid Patients and depicts eight Hungarian cities. It measures 14.40 m (47.24 ft) in length and 6 m (19.69 ft) in height.
For a complete list of 2013 records, please visit 2013 Guinness Records in Hungary.