The crypt is the oldest part of the church and the high altar supposedly contains the bones of St. Minias (they may have been removed to Metz.)

Buildings in Tuscany were conservative and followed Early Christian models. An important feature of Florentine Romanesque is exemplified by the striking use of coloured marble inlays to form lively geometrical patterns seen also at S Miniato al Monte, with an interior articulated by the rhythmic alternating system of columnar and quadrilobed piers, the latter rising to diaphragm arches.