This project studies the geological exploration of the Balkan Peninsula, focusing on descriptions and analyses of thermal water produced by traveling naturalists and scientists from the early sixteenth century to the late nineteenth century. The project examines how the exploration of the thermal hydrology of the Balkans was situated in the broader study of the peninsula and how it influenced travelers’ perceptions of Balkan societies and cultures. Having already studied the early modern period with a fellowship from the Centre for Advanced Study Sofia, as a NEC fellow I will focus on the nineteenth century, the “golden age” of geology, when the thermal water resources of the Balkans were surveyed by some of the leading European geologists. I am particularly interested in examining the works of Ignaz von Born, Johann Ehrenreich von Fichtel, and Belsazar Hacquet on the geology of Transylvania and the Carpathian Mountains. I want to compare their observations with those of Ami Boué and Ferdinand von Hochstetter, who conducted geological fieldwork in the Ottoman Empire’s European territories. Such a comparison could provide valuable insights into whether the different political and religious contexts of the lands north and south of the Danube produced epistemological distinctions in the study of their hydrothermal landscapes.