There are many stories and legends about Emperor Diocletian, some of them related to Split and Dalmatia. For example, walking at the western end of Riva promenade always brings not so pleasant smell. It's neither sewage nor pollution, but one of possible reasons for Diocletian to build his retirement home right there. Namely, one of those stories about Diocletian - accepted even among historians - says that he chose this location because of sulphur springs, with water helping him to cure his rheumatism. Even Emperor's biographers wrote about his medical problems, for example Lactantius or Eutropius. That was the reason for thermae built in the south-western part of the Palace, with water rich with minerals, and used by the aging Emperor as a cure. He also paid attention to his guests, who had another bath house on their disposal, in the eastern part of the Palace, next to the dining hall. And there are even more important connections between Diocletian and thermae; those in Rome bearing his name were the biggest ever built in the whole Empire.
This can make someone to conclude that Split is by its "genes" God-given place to cure body and soul.
Diocletian was only one, maybe even not the first one, of those who enjoyed all the benefits of healing springs. Monks in the monastery of Saint Francis at Riva used them, same as local housewives and maids for bleaching their laundry, or guests of the fancy bath house with stone made bath tubs built by wealthy Split-native Nikola Selebam. It's worth of noticing also beautiful building of old spa in Marmont street. Its water was highly recognized and awarded in Vienna, Rome, London, Paris, Brussels, even in the USA. Viennese university did a research in the early 20th century and draw a conclusion that mineral water in Split is the best in Europe. Croatian painter Radovan Tommaseo even designed posters to attract early 1900's wellness fans. At its peak in 1913, spa hosted up to 300 people a day.
Today, the rehabilitation centre of the local hospital occupies the old spa, but there are so many other elements in favour of curing image of Split. If you find that smell at Riva unpleasant, although completely natural, Split still has excellent spring water, coming from river Jadro ever since Diocletian's times. And even if you don't use any of wellness centres in local hotels, let's not forget clean and clear sea, many unspoiled spots to enjoy nature, healthy diet, etc.
And all that can be put in only one sentence; Split is a cure.