Already known to the Romans, the thermal spring of Equi owes its fortune to the engineer Carlo Tonelli who, in the late 19th and early 20th century, saw its therapeutical potential and decided to exploit it by building a thermal centre. Thus it was that, in 1894, in the vicinity of a picturesque old village, the Equi centre was established. Site of the XX National Conference on Medical Hydrology and Climatology (1929), the thermal centre was managed continuously by the Tonelli family until 1989, the year in which it became the property of the Commune of Fivizzano.

Today the modern thermal baths, thanks to their sulphurous water, continue to cure visitors affected by respiratory and bone and joint disorders, while offering, thanks to their position, the chance to take interesting excursions. One of the most interesting of these is a visit to the nearby karstic zone called "La Buca", in the Apuan Mountains Park, whose caves filled with stalagmites and stalactites attracted the attention of the great naturalist Antonio Vallisneri in the late 18th century.