Originally the family mansion of St. Cecilia, it was converted into a church by St. Urban in 230, in accordance with her dying request. The approach is by a spacious courtyard, on the right of which is a large marble cantharus, or vase, belonging probably to the original palace. The bell tower dates from 1120.

The delicate carving of the drapery should be noticed. The Blessed Sacrament is usually reserved in the first chapel of the right aisle. Next to this is the Caldarium, or bathroom, where St. Cecilia was martyred, with the original pipes along the wall for conveying steam from the boiler. The marble slab on the altar is the one on which she was struck by the executioner, and above it is an exquisite painting of her martyrdom by Guido Reni. On the opposite wall a striking picture, by Domenichino, represents an angel crowning Cecilia and her young spouse Valerian.
 

Martyrdom of St. Cecilia , A.D. 230. - Cecilia alone remained, and as Almachius, the judge, thought it best that her punishment should be as secret as possible, he ordered that she should be shut up in the Caldarium, or room of the warm bath in her own palace and that the pipes with which the walls on all sides were perforated, should be heated to such a degree as to cause suffocation. Cecilia entered the room the furnace being heated, and though she remained there for a whole day and night, she was found to be unhurt by the hot steam that scalded those who opened the door. Almachius then sent one of the lictors with orders to strike off her head.

Three times did the axe fall upon her tender neck, inflicting deep and mortal wounds, but without severing the head. As the law did not allow more than three strokes to be given, the executioner went away, leaving her still breathing and bathed in her own blood. The faithful of her house and neighbourhood then flocked into the room to receive the last breath of the dying martyr. For two days and nights, she continued hovering between life and death; and on the third morning the venerable Bishop, Urban came to take leave of his beloved daughter. Her dying request to him was, that the poor she had always loved should be cared for and that her house should be made a church forever. Soon after she breathed forth her pure spirit to God. 

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The body found incorrupt in A.D. 1599. Nearly eight hundred years afterwards, Cardinal Sfondrati, of the title of St. Cecilia, made considerable alterations in the church, and in course of his excavations in the sanctuary, came upon a wide vault beneath the altar. Two marble sarcophagi met his eyes. Trustworthy witnesses had already been summoned, and in their presence one of these sarcophagi was opened. It was found to contain a coffin of cypress wood . The Cardinal himself drew back the coffin lid. First appeared the precious lining and silk gauze with which Paschal had covered the body nearly eight centuries before. Its colour had faded, but the fabric was still entire, and through its transparent folds could be seen the shining gold of the robes in which the martyr was clothed. After pausing a few moments the Cardinal gently removed this silken covering, and the virgin form of St. Cecilia appeared in the very same attitude in which she had breathed her last on the pavement of the house, and which neither Urban nor Paschal had ventured to disturb. Lying on her right side, with her arms extended in front of her body, she looked like one in deep sleep. The head was turned downwards, the knees were slightly bent. The body was perfectly incorrupt, and by a special miracle retained, after more than thirteen hundred years, all its grace and modesty, and recalled, with the most truthful exactness, Cecilia breathing forth her soul on the pavement of the bath.

All Rome came to see the virgin martyr, whose body lay exposed for veneration for the space of four or five weeks; and when the tomb was again closed on St. Cecilia's day, 1599, the Pope himself sang the Mass. Cardinal Sfondratierected the beautiful high altar which now stands over the Saint's tomb, and beneath it be placed an exquisite statue by Maderno, the foremost sculptor of the day, who had frequently seen the body, and made an exact copy of it in the very posture in which it lay.