Ankylosing spondylitis (also known as Bekhterev's disease), in particular, has been claimed to see positive results from treatment at the Heilstollen. However, there is no empirical evidence of any benefit to inhaling radon. For example, one of the few studies to test the efficacy of spa treatments for ankylosing spondylitis found no statistically significant difference between a group that spent three weeks at Bad Gastein and a group that spent three weeks at a different spa without radon inhalation therapy. Claims of therapeutic benefits of radiation, beyond its application in radiotherapy, are considered quackery by medical professionals. History The remote valley was settled by Bavarian peasants in the 9th century; field names in the highest-lying southern parts also denote a Carantanian (Slavic) colonization. Gastein is first mentioned as Gastuna in a 963 deed, when the area belonged to the German stem duchy of Bavaria. It was originally an alpine farming and gold mining area and the site of an ancient trade route crossing the main ridge of the Central Eastern Alps. In 1297 Duke Otto III and his brother Stephen I, both highly indebted, sold it to the Prince-Archbishops of Salzburg. Already about 1230, the minnesinger Neidhart von Reuental had referred to the hot springs in his Middle High German poem Die Graserin in der Gastein; the spas were visited by the Habsburg emperor Frederick III as well as by the Renaissance physician Paracelsus. In the 19th century the waters of Bad Gastein became a fashionable resort, visited by European monarchs as well as the rich and famous. Some notable guests of the past included Empress Elisabeth of Austria (Sisi) and the German Emperor Wilhelm I with his chancellor Otto von Bismarck as well as Subhas Chandra Bose, a leading Indian nationalist, Tsar Ferdinand I of Bulgaria, King Faisal I of Iraq, King Ibn Saud of Saudi Arabia and Iran's last king Mohammad Reza Pahlavi, industrialists like Wilhelm von Opel and artists like Heinrich Mann, Robert Stolz and W. Somerset Maugham. On 14 August 1865 Bismarck had signed the Gastein Convention with Austria concerning the joint administration of the provinces of Schleswig and Holstein after the Second Schleswig War. The composer Franz Schubert composed his Piano Sonata in D Major in Bad Gastein, and was once believed to have sketched a Gmunden-Gastein Symphony (D. 849) during his stay in August and September 1825. Though no score appears to have survived