The Lutheran church of Saint-Martin in Montbéliard (Doubs) is considered the oldest French Protestant building still existing today after the destruction of the great French Reformed churches of the sixteenth century by the royal powers. It is of original architecture, standing out by the specific basilica layout (i.e., the so-called Reformed choral quadrangle) and its Nordic Lutheran axial plan. Recent archaeological work has unveiled very interesting wall decors from 1607 and 1741. The discovery of this original layout is reason to revisit the common view of French Protestant architecture, which can no longer be reduced to the architecture of the nineteenth centred with the pulpit at its centre and austerity and severity as its main marks.