The Abbey, erected on Via Cassia and now incorporated into the urban center of Montale, is documented as far back as 772 as a Lombard monastery with a prevailing function as a hospitium for wayfarers and pilgrims. It rises near the lowland outlet of the Apennine stream named Agna stream, to which the town’s name refers.
Managed by the Benedictine monks from 1028 to 1429, then by the Canons Regular of the Lateran until the 16ᵗʰ century, it was subsequently closed to worship and converted firstly into a wine cellar then a silkworm farm. In 1778, it passed to the Grand Priory of Cortona then to the Covoni and Borghese families until recently becoming the property of the Pistoia church.
The Abbey was almost completely restored in the 1920s.
Of the original structure, the crypt is preserved, dating from the 10ᵗʰ to 11ᵗʰ centuries, with richly carved columns and truly valuable capitals.