The Antico Borgo Chieti is near the site that houses the cathedral church of Theatine. Leaving aside the hypotheses on any pre-existing classical or early Christian, we are aware of the consecration of a new building dedicated to St. Thomas the Apostle by the bishop Attone I in 1069 (November 5).
Source on the remains of two pre-existing factories, whose structure is unknown to us; one of these was probably destroyed in the fire that Pippin set on the city in 801, the other collapsed at an unspecified date, after it was built by the bishop of Chieti Teodorico I, of Frankish origin (840).
The Attone factory must have had its present orientation, although it has not reached us in any way, if not (perhaps), in some element of the crypt, renovated in the fourteenth century, to which we owe the construction of the first three floors of the Bell tower.
In 1498, Antonio da Lodi will add the top floor and the cusp. The building began to take on today’s features at the turn of the seventeenth century, when the archbishop-count of Chieti, Matteo Seminiato, proceeded to a first major restructuring, to which others will follow also because of the ruined earthquakes that struck the area ( first of all the famous earthquake of 1703).
It is in this period, among the archbishoprics of Monsignor Francesco Brancia (1769) and Luigi Ruffo Scilla (1881), that the church takes on the delicate forms of the late Baroque that distinguish the interior.
Between 1920 and 1936, the arrangement that revolutionized the façade and side of the cathedral (which is what the church shows in the square) was designed and built by Guido Cirilli, redesigned in medieval forms inspired in part by the few elements of the decoration coeval survivor in the apse, in part more conspicuous than Romanesque examples of the southern Adriatic area. The side entrance (originally accompanied by a staircase and a portico) is eliminated, a new portal is drawn, always tangent to the actual entrance, a new façade for the transept, while the church and bell tower were incorporated into a marble plinth and the bell cusp fell in 1706 due to the earthquake.
In the seventies, the policy of “restoration” then pursued by the regional superintendence, destroys the baroque decorations of the crypt, bringing to light the underlying medieval “layer” of exposed bricks and only a few traces of frescoes.