(Collecta: Ss. Cosma e Damiano)
The collecta of Ss. Cosma e Damiano to the left, and the statio of San Clemente to the right
From Blessed Ildefonso Schuster's The Sacramentary:
The Basilica of St. Clement rises on the site of an ancient Roman domus, which a well-founded tradition connects with the Pope of that name. There is nothing unlikely in the story that Clement, in the days following the Neronian persecution, gathered together the scattered flock of Christians under the very roof of the house which we visit today...
From the Churches of Rome wiki:
The present San Clemente was built around 1100. Below it is a 4th century church, and below that a Roman house in which it is believed Christians worshipped until the 4th century church was built.
The oldest level is thought to be the titulus Clementis, one of the first parish churches in Rome, and probably belonged to the family of Titus Flavius Clemens, consul and martyr and a contemporary of Pope St Clement. The church was set right next to a pagan temple, a Mithraeum or Temple of Mithras, which is also preserved.
A proper church was built after the Edict of Milan was passed in 313, allowing Christians to practise their religion openly. The first written evidence of this church comes from the pontificate of Pope Siricius (384–399), when a church dedicated to St Clement is mentioned. The older buildings were filled in, and a church occupying about half that area was built. The Mithraeum continued to exist until 395, when all pagan cults were outlawed. The property was taken over by the clergy of San Clemente, who filled it in as a foundation for an apse to the church.
Pope John II (533–535) was a great benefactor of the church - he had been cardinal priest of San Clemente from c. 532 until his election as pope in 533. His name can be seen inscribed on several slabs in the church.
The church was severely damaged by the Normans under Robert Guiscard in 1084. It became unsafe, and the titular priest of the church, Cardinal Anastasius filled it in and had a new church built.
Pope Clement XI (1702–1715) had the church restored, with Carlo Fontana as architect.
The first excavation of the lower church was carried out by Fr. Joseph Mulooly O.P. 1857–1870, with the cooperation of Giovanni Battista de Rossi. Fr. Louis Nolan O.P. carried out further excavations 1912–1914, and since then more or less continuous work has been going on.
