The area
The area (in Campo Marzio) included between the far-reaching extensions of the Campidoglio and the Quirinale and the Tevere, exterior to the city and to the pomaerium, all over the ancient time, is characterized by two operations: the domaniality and the military exercises. The name itself of Campo Marzio derives from these activities and linked to them is the presence of theold sanctuary of Mars.

But the area was filled all along the republican and imperial era with other monuments related to new cults and the space, more and more restricted itself for the military exercises. They were confined in the zone of the loop of the Tiber ; infact it was the only one which kept the name of Campo Marzio, even in medieval and modern period.
The main function which characterized the Campo Marzio zone was the one dealing with vote operations for the magistrature. For that purpose, the Saepta Julia square was set up, and with other edifices it made a complex for meetings and vote operations.
The meridional zone of the Campo Marzio saw the development, in the last two centuries of the Republic, of an intense activity of monumental building promoted by the senate aristocracy : temples were built: the temples of Ercolese and of the Muses (187 a.c.), of Giunone the Queen (179 a.c.) and the porches of Octavius (168 a.c.) and of Metellus (146 a.c.). Very important has been the construction of the Theatre by Gnaus Pompeius which later took its name from him. The construction of Balbo theatre (13 a.c.) constitutes the last monumental intervention of a member of the aristocracy extraneaous to the imperial family. In fact Augustus will continue the construction work of the zone with the construction of the theater of Marcellus and with the remaking of the temples of Apollo and Bellona and of the porch of Metello dedicated to Ottavia, sister of Augustus.
Thus begins a period in which it will be characters tied to him (as the son-in-law of Agrippa) who will bring about the construction of an impressive series of monuments which will redesign the entire Campo Marzio. Beyond those cited and the remaking of the Saepta and of the related edifices, to those interventions is due the construction of the thermae of Agrippa, the first public thermae of Rome, of the first stable amphitheatre, the one of Statilio Tauro ; of the Pantheon, of the Ara Pacis, of the great solar clock. With the construction of the mausoleum for himself and for the members of his people, Octavian put the definitive seal to this reappropriation in "chiave augustea" of the entire Campo Marzio.

From the republican era even the Villa Publica (central zone of the Campo Marzio, included between the Circo Flaminio and the complex of the Saepta and of the out-buildings) which, beyond carrying the function of public park, was also the centre of some quinquennial centuring functions and in the interior of which rose the sacred area of the Argentina square it began to be occupied by temples, porches and by other monumental edifices.


Largo Argentina's Post classical phases
In the course of the 5th century the northern porch was restored, may be destroyed by an earthquake and the passages between the pilasters which marked the oriental limit of the area were risen by about 60 centimeters.
Other great transformations during the same period were made : near the area sacra, where was established the Xenodochium Anichiorum, a complex destined to the welcoming of poor people and pilgrims. In the first years of the VIth century the 'Area Sacra' underwent a deep transformation from which little has remained of that period.
Anyhow the passages between the pilasters of the oriental limit were closed, isolating the area toward the exterior thus losing the character of public place. Were closed also the intercomuns of the small northern porch which became a covered corridor. The structures between the temples were covered with a flooring in travertine on which were erected rooms lined up along a corridor.



In front of the A temple, was uilt a large rectangular hall divided in two by a line of pilasters and with a long bench which extended along the walls. This complex, perhaps, was a monastery and the small rooms along the side of the A temple , and behind the B temple probably were monk sells. May be the oratory of the monastery was founded in the A, where, in the temple following centuries would be built a church.
In fact the edifice in the interior of the sacred area probably was an ancient monastery as quoted in the 'Liber Pontificalis', "monasterium Boetianum', may be linked with the philosopher Boezio.
To the successive phase of transformation of the VIII-IX century is imputable the pulling down and the burying of the large hall in front of the A temple, the heightening again of the shuffle plan of about 1.20m. in the area in front of the A temple, and the construction of a serie of structures in tufo blocks pulled down in the assessment of the area in 1929. These structures may be were residences of the aristocratic people and changed the structure of the area which no more lived as an unitarian complex.
The caroline age represents the moment of the breaking off of the plan inherited by the ancient city with the creation of the net work of streets, squares and lanes of the new city. To the same period must be ascribed the first archeological proofs of the installation of a church in the interior of the A temple. The foundation of the apse is infact built in the same technique in tufo blocks the used again of the other structures ot that phase, and also the semi-annular crypt has a characteristic typology of the churches datable at the caroline age. The district, as always in the medieval city, was characterized by a great social promiscuity, on account of which craftsmen, merchants and aristocrats lived side by side, naturally they were distinguished by the wealth in respective houses.
In the middle ages the church of the A temple underwent alterations: to the 1132 is attributed the actual lay out of the apse and of presbytero, the altar with cippuses still visible, the frescoes of the apsis and a restructuration of the crypt.
In the XIVth century the church was enlarged and was created the small lateral apse and the abandon of the crypt.
In 1132 the church was dedicated to Saint Nicolas whose cult was propagated at that time in Italy.