Most caves in Emilia-Romagna are developed in Triassic and Messinian gypsum outcrops. These evaporite rocks, although representing only around 1% of the surface outcrops, host over 600 caves, among which the longest epigenic cave in the world (the system Spipola-Acquafredda close to Bologna, with over 11 km of surveyed passages) and the deepest one (the Monte Caldina system, 265 metres deep). Because of the fast dissolution of gypsum these caves have always been considered as having formed rather recently (last 20,000 years, or slightly more). In presence of important concentrations of CO2, from the waters saturated in calcium and sulphates flowing in these caves, calcite is precipitated leading to the formation of carbonatic flowstones. These speleothems, known from many caves of Emilia-Romagna, can be dated by the U/Th method, giving a minimum age of the formation of the passages in which they deposited. In the framework of two PhD theses, calcite flowstones have been sampled and dated in a dozen of caves and surface locations in the Vena del Gesso Romagnola, and in the gypsum areas close to Bologna. These analyses have identified flowstones with ages as old as 316 ka, demonstrating some caves to have existed since then. The oldest still active cave system is Re Tiberio, in the Vena del Gesso, that started forming at least since 130 ka.