Sant’Elena dei Credenzieri was a small late 16th century confraternity church, now demolished, on the present site of the Largo Arenula. This is in the rione Sant'Eustachio.
The earliest documentary reference to the church dates from 1186, when it was described as a chapel dependent on San Lorenzo in Damaso and having the name San Niccolò de Mellinis. At some stage in the Middle Ages it became parochial, and the name settled down to San Niccolò dei Molini. It was also known as dei Cavalieri, after a noble family which had its palazzo on the piazza in front of it.
In 1577 the church was given into the care of the Confraternita dei Credenzieri, which was the guild of butlers or housekeepers serving the nobility (literally, “keepers of the sideboard”). In 1594 the confraternity appointed one Francesco Ferrari (not to be confused with the 17th century painter) to rebuild the church entirely, and simultaneously obtained the suppression of the parish. They also re-dedicated the church to their patron, St Helen.
The French occupation was not kind to the confraternity, and they dispersed at the start of the 19th century. The vacant church was then obtained by the Arciconfraternita di Gesù Nazareno, which remained in possession until the church was demolished.
This happened in 1888 for the building of the Via Arenula. Its companion church of Sant’Anna dei Falegnami, which was on the other side of a small piazza to the south, was also destroyed at the same time. The archconfraternity moved to the present church of Gesù Nazareno all'Argentina, which is nearby.
The site is marked by the circular newspaper kiosk to the east of the largo. Before the Largo di Torre Argentina was laid out as the city end of the Via Arenula, the Via delle Botteghe Oscure used to come to a stop in a little piazza latterly known as the Piazza di Sant'Elena. The portion of the street west of the junction with Via Paganica used to be called Strada Florida, and this is now Via Florida. The church occupied the south side of the piazza.
The kiosk sits exactly on the site of the former piazza outside Sant'Anna, so the main altar of Sant' Elena used to be just to the north.
The church survived long enough for photos of it to exist. See the de Alvariis gallery on Flickr; the photo there taken at an angle shows the pediment of Sant'Anna behind.
It was a tiny, charming edifice already dwarfed by the surrounding domestic buildings in the late 19th century. The plan was a simple rectangle, without external apse or side chapels.
The façade had two storeys, and was in a very restrained Baroque style. The first storey had no pilasters, but instead three gigantic vertical rectangular recessed panels, with stepped edges. The central, wider one of these had the entrance, which again was very simple with a raised cornice supported by a pair of block corbels. The top of the storey was marked by an entablature with a dedicatory inscription mentioning the saint.
The second storey was itself divided into two sub-storeys by a cornice running the width of the façade, and having a shallow curve over the head of a large window in the centre. This was flanked by two horizontal rectangular panels of the same style as the ones below, but much smaller. Above the cornice was a plinth with flaming urn finials at the ends, and above the window was a large aedicule framing a fresco of the Discovery of the True Cross by St Helena. This was topped by a triangular pediment, and flanked by gigantic volutes. The pilasters supporting the pediment did not have proper capitals, but were decorated at the top with tassels instead.
There were two side altars, although no proper side chapels.
The main altar had a depiction of the patron saint from the school of Pomarancio (which one?). Of the two side altars, one was dedicated to the Assumption with an altarpiece by Orazio Borgianni, and the other was dedicated to St Catherine of Alexandria with an altarpiece by the Cavalier d'Arpino.
The latter altar was a descendant of one that apparently was attached to the medieval church from early times. To the right of it was preserved an inscription kept when the church was rebuilt, which read:
Antiquissima cappella S[anctae] Catherinae de iure patronatus domus Cavalerorum quae cum vetustate iam fere esset collapsa, Tiberius Cavalerius, canonicus Lateranen[sis] ac eiusdem cappellae possessor in ampliorem locum et meliorem forman posuit, a Nativitate Domini MDLXXXXI D[ie] P[rima] Apr[ilis].
("The very old chapel of St Catherine, in the care of the family of the Cavalieri, Tiberio Cavalieri the Lateran canon and the owner of the same chapel, rebuilt in a bigger and better form from Christmas to the first day of April, 1591. It had almost fallen down with age.")
Also in the church, situated in the apse, was a little shrine with closing doors which contained a fresco of the Holy Family.