The most interesting and imposing building in the city of Heidelberg is the castle. Although devastated by the French in 1689 and 1693 and then struck by lightening in 1764, this magnificent red sandstone structure, 330 feet about the river, still dominates the city. Construction began in the 13,h century, but the most notable work was done in the Renaissance period and includes the Otto-Heinrichsbau and the Friedrichsbau wings. In the cellar of the latter is the Heidelberg Tun (1751), an enormous wine cask with a capacity of 49,000 gallons. The castle can be reached fr om the lower city by a cable railway, which continues to the summit of the Konigsstuhl (massif).
A publicity show was sponsored on 20 April 1941 (Hitler’s 52nd birthday) by the KdF Stamp Collectors Club of Heidelberg wh ere the special postmark was used.