Salse di Nirano natural reserve, Regional nature reserve in Fiorano Modenese, Italy.

Salse di Nirano is a regional nature reserve in the hills of Fiorano Modenese, where cold clayey mud rises from underground along fractures and faults, mixed with methane and salt water. The mud dries into pale grey cones a few metres high, built up between the continuous supply of mud and its erosion by rain. The field lies on the floor of a sub-circular depression crossed by a tectonic step that divides it into two blocks 10-15 metres apart.

The reserve was established in 1982 as the first regional nature reserve in Emilia-Romagna, and since 2004 it has also been a Site of Community Importance. Its mud springs rise along fractures and faults from Pliocene blue clays laid down on the floor of the ancient Adriatic Sea, which then covered the Po Plain. The mud is cold and mixed with methane and traces of liquid hydrocarbons.

The name salsa comes from the Latin salsus, meaning salty, after the sodium chloride in the mud, which leaves white efflorescences when it dries. The reserve's services are based at Ca' Tassi, a restored rural complex and the region's first energy self-sufficient visitor centre, with a natural history museum and laboratory. Since October 2010 the nineteenth-century Ca' Rossa farm houses the Ecomuseo.

The reserve has marked paths with information panels that make exploring easier and help you understand the formations. The best time to visit depends on weather, as rain can make the paths difficult to navigate.

The mud field sits in a sub-circular depression, and a tectonic step of 10-15 metres splits it into two blocks along a NW-SE line. The mud is cold clay mixed with methane and traces of liquid hydrocarbons, which leave brown oil patches on the surface.