Santa Maria della Purità in Borgo was a small church or chapel, now demolished, in a very narrow alleyway running north of the Borgo Nuovo. This street is now the Via della Conciliazione.
The dedication was to the Blessed Virgin Mary, under her title of Our Lady of Purity.
It is thought that the site of the chapel was originally that of a church called San Sebastiano in Via Pontificum. This was reported in ruins in the reign of Pope Pius V (1566-72). Via Pontificum later became the Borgo Nuovo.
The chapel was founded in 1591, was dedicated to St Sebastian (hence the hypothesis mentioned), and was intended for the use of the Confraternita del Santissimo Sacramento. This in turn had been founded by some pious laymen of the locality to assist in the cult of the Blessed Sacrament, especially as regards processions and visiting sick people. The foundation legend was that a priest was taking the Blessed Sacrament to a sick woman, and the candle held by the acolyte accompanying him failed. So, they had to go into a shop to obtain a new one. This was regarded as scandalous, hence the confraternity was founded so as to take better care of the Sacrament.
In 1601, the confraternity moved to the Blessed Sacrament Chapel at the nearby San Giacomo a Scossacavalli, which they had built for themselves. The chapel was then passed on to the Collegio dei Caudatari dei Cardinali, which re-dedicated it to Our Lady of Purity and enthroned an icon of her over the altar. A caudatario was a ceremonial functionary who held up the parts of the garb of prelates that would otherwise drag on the ground -a trainbearer in English.
The Caudatari did not take very good care of the chapel in the 19th century, because it was in such bad repair in 1897 that the icon was removed to the nearby church of Santa Maria in Traspontina and the chapel was deconsecrated. It was a warehouse until the site was cleared during the building of the Via delle Conciliazione in 1938, and a modern block erected on it.
The chapel stood on the right hand side of a very narrow alleyway, the Vicolo della Purità, which ran north-westwards from a point on the Borgo Nuovo about where the left hand corner of the rebuilt Palazzo dei Conservatori now is. It emerged on the present Via dei Corridori, between the junctions with the Via Rusticucci and the Vicolo delle Pallini.
Halfway along from the Borgo Nuovo, the alleyway bent to the right through a very tight archway before resuming its course. The chapel entrance was to the right of this.
The site is now in the middle of the large block to the west of the Palazzo dei Conservatori, and is inaccessible from the street. It lies behind the rusticated archway to the left of the Caffe San Pietro.
No description of the chapel interior seems to be available. It had the plan of a transverse rectangle, with a tiny shallow rectangular apse.