and the country's first indoor swimming pool. The park was also enlarged. A railway to Thionville was opened in 1903 and, in 1913, the Marie-Adélaïde Source, named after the grand duchess Marie-Adélaïde was added after drilling to a depth of 464 metres. After a quiet period during the First World War, a new spa centre designed by architect Paul Wigreux was opened in 1926. In the 1930s, the hotels were occupied not by visitors interested in the waters but by émigrés from Nazi Germany. At the same time it was visited by Polish pianist Arthur Rubinstein. During the Second World War, well-to-do Nazis enjoyed relaxing at "Staatsbad-Mondorf", far away from the bombing and fighting. In 1945, Mondorf's Palace Hotel became Camp Ashcan, a prisoner-of-war camp for senior Nazi dignitaries who awaited trials at Nuremberg. During the Allied occupation, that lasted until September 1945, there was no permission to transit in the town from 7 pm to 7 am. The spa continued to prosper in the second half of the 20th century with an outdoor swimming pool (1953), a new thermal centre (1988), and the Casino 2000 which opened in 1983. Spa facilities The spa welcomes thousands of visitors a year with its richly mineralized waters at . Set in a park of 36 ha (89 acres), its facilities are among the most modern in Europe. The waters are particularly suitable for the treatment of liver, gastric and respiratory ailments. In addition to a fully equipped fitness pavilion, there are also massage booths, saunas, indoor and outdoor swimming pools, solariums, Turkish baths and whirlpools. Treatments from algae wraps and lava-stone therapy to lymphatic drainage and ayurvedic rituals are said to be especially relaxing. The church St Michael's Church is one of the country's finest Rococo buildings. Inside the church, the fresco, pieta and pulpit are of special interest. Now a listed building, the church was built from 1764 to 1766 on the initiative of Nic Ungeschick, with the support of the abbey of Echternach. The Louis XV furniture was created by the local sculptor Jean-Pierre Decker who lived and worked in Mondorf. The organ on the balcony with musical emblems, the confessionals and the altars blend harmoniously with the frescos designed by Weiser from Bohemia. The original St Michael's was built in 1065 but was destroyed and rebuilt on several occasions. Population Economy The major contributor to Mondorf's economy is Casino