
The health resort dynamically developed in 1930–1939, with new boarding houses and modern infrastructure being built (a post office, numerous shops and restaurants, a railway connection to Poland’s main cities, including Lwów). The Iwonicz Spa Committee (est. 1923) coordinated the health services and hotel accommodation, as well as running the spa treatment fund.
The Excelsior Sanatorium, which opened in July 1931 after many years of construction work, was Iwonicz’s first (and one of Poland’s first) all-year-round public property institutions of this type. The patients were either Sickness Fund insurance holders or commercial customers.
its own electric power and gas unit, a natural therapy facility, an X-ray studio, an operating theatre, doctors’ surgeries, treatment rooms, and facilities such as a laundry, workshops, and cold store. An own sewage treatment plant was an innovation, and the upper floor solarium was unique among European health resorts.
Józef Koffler underwent treatment at the Excelsior at least twice (1935 and 1937), most likely for arthritis. In 1937, he spent part of his vacations with Adam Mitscha. He probably not only drank the local medicinal waters and bathed in them, but also took advantage of the fine air, with high levels of iodine and bromine.



