The basilica of "St. Bartholomew at the Island" was built around the end of the X century (in 997, according to Gregorovius) wish of the Germanic emperor Otto III, in honor of his friend martyr St. Adalbert, on the ruins of an ancient Roman temple dedicated to Aesculapius (they say that Otto chose the Tiber island to be able to see the church from his building on the Aventino).
Otto III endowed the basilica with relics of saints, among which those of St. Paolino from Nola and the apostle Bartholomew. Subsequently the name of the basilica changed from Adalbert to Bartholomew: already in 1088, on some documents, it is named S. Bartholomeus a Domo Ioanni Cayetani [St. Bartholomew near Ioanni Cayetani house] and an inscription dated 1113, the lower one on the inlet portal of the basilica, testify the presence of the bodies of St. Bartholomew and Paolino from Nola only. (pict.1)
During the pontificate of Pasquale II (1099-1118) the church was completely rebuilt, as testified in the upper inscription on the same portal; probably also the Romanesque bell tower at church side dates back to that time.
The rebuilding activities ended in the second half of XII century, during the pontificate of Alexander III (1159-1181), and brought the main aspects of the church to the present configuration.
Cardinal Title in 1517 for will of pope Leone X, in 1524 the church of St. Bartholomew was entrusted to the Franciscan Observant Friars.
During the pontificate of pope Giulio III (1550-1555) the Corporation of Milled established their religious see in the chapel at the left of the main altar, remaining there up to 1846. In 1557 a disastrous flood irreparably damaged the façade and its mosaics, the right aisle and the presbytery area, also destroying the pictorial and mosaic decoration of the inside; only a fragment has been preserved, now in the Room of the Mosaic, previously monks' choir, above the portico (fig.2). The church was then temporarily disused and the relics moved to the Vatican Basilica. In 1583 the cardinal Anton Giulio Santoro sponsored the restoration of the façade, the right aisle and the presbytery, the construction of a new ciborium in place of the medieval one (of which re-used the four precious columns in porphyry, then moved in 1829 in Vatican in the Tapestries Gallery) and the return of the apostle Bartholomew relics from the Vatican Basilica. The relics were deposed in the ancient red porphyry basin that still today is the base of the main altar. (fig.3)
In 1601 the relics of St. Paolino and the holy Adalbert, Esuperanzio and Marcellus were located in the Milled chapel; in the 1636 St. Paolino from Nola became the patron saint of the Milled.
From 1608 to 1621 the cardinal Michelangelo Tonti called Anthony Carracci (1589-1616), nephew of Annibale, to fresco four of the six lateral chapels of the basilica.The construction of the new façade, the wooden ceiling and some other smaller interventions were carried out at the time of the Spanish cardinal Gabriele Trejo Paniacqua (1621-1630).The Cardinal Nephew Francis Barberini financed in 1638 the construction of the Franciscan convent wing at the left of the façade (1639), symmetrical to that built in XVI century and now demolished, but visible in some old engravings. (fig.4)In the appurtenances of the basilica the Franciscans established in 1694 their Missionary College, operating up to 1885 when it was dispossessed by Italian government.In the first decades of XVIII century the Spanish cardinal Anthony Cienfuegos, titular from 1721 to 1739, promoted and financed the arrangement of the access balusters to the chapels, the floor and the rich plaster decoration that decorate the complete central nave of the basilica.In the XVIII century some important religious institutions were established in St. Bartholomew among which the Brotherhood of the "Devoti di Gesù Crocifisso al Calvario e di SS. Maria Addolorata" [Devouts of Jesus crucifix at Calvario and of Our Lady of Sorrows], so called of "Sacconi Rossi" [Big Red Sacks] for the characteristic habit used during the processions, founded in 1760, whose members entrusted themselves to pick up the abandoned corpses and in particular the ones drowned in the Tiber, burying them in a cemetery below the oratory.In 1798 the church was occupied by the French army; the damages caused by the military occupation made necessary, in 1801, the restoration of the presbytery area. In the 1852 the pope Pious IX (1846-1878) donated a new altar to the church, arranged around the porphyry basin with the relics of the apostle, and ordered a campaign of works in the years 1865-68, promoting a money collection for the purpose.During the terrible months from September 1943 to June 1944 the basilica, similarly to the convents and religious houses in Rome, was the refuge of several Jews, hidden to avoid deportation.In 1994 pope John Paul II entrusted the basilica and the relevant appurtenances to the Community of Sant'Egidio, and since 2000 it is dedicated to the “New Martyrs of the XX century” (pict.5).