The term “pieve”( parish), from the Latin word plebs (people), has indicated since the V-VI centuries the faithful close to a foundation or matrix church ruled by a presbyter and having a baptistery with a christening font and consequently called also “baptismal church”. Afterwards, the term was employed to indicate the territorial circuit the congregation lived within: those districts had as chief town the village where the only church with a christening font was. The pieve of Mazzo, of ancient origins, stretched from Serravalle gorge (at the gates of Bormio’s countryside) up to the municipality of Sernio, just above Tirano, and bordered with the pievi of  Bormio, Villa di Tirano and Poschiavo.