According to tradition it was founded by the emperor Constantine in 320 using one large chamber of the Sessorian Palace to house the relics brought by his mother Helen from Jerusalem. After the edict of Milan which in 313 declared freedom of worship even to Christians, Rome became the new capital of Christianity.
In order to give a special value to this decision relics of Mary, Christ and the Apostles were bought from Palestine. These interests gave life to a new commerce and as usual the market offered also many fakes. S. Croce in Gerusalemme became so the basilica of the relics.
Here are kept soil from the Holy Sepulchre, fragments of the Holy Cross, two thorns from the Crown, the crosspiece from the cross of the penitent robber who was crucified beside Christ and many other venerated objects. The church was restored in 1144 by Lucius II. In 1743 by wish of the pope Benedetto XIV it was completed renewed by Gregorini and Passalacqua. It is one of the 7 churches which are jubilee destinations during the Holy Years.
The façade dates back to the XVIII cent. by Gregorini, who inspired himself to the concave-convex style of Borromini. The interior is divided into three naves with apse and transept. The medieval cosmatesque style floor is very well preserved. Beside the pilasters there are eight granite columns from the ancient basilica. At the beginning of the main nave there are two holy water stoops dating back to the 1400’s with fishes sculpted inside.
The canopy dates back to the 1700’s, in the apse there is a beautiful tomb of the 1400’s by Sansovino. A staircase of the XV cent. leads to St. Helen’s chapel decorated with a beautiful mosaic by Melozzo da Forlì. Beside the church there is a monastery run by Cistercenses monks built at the end of the X cent. Inside there is a wonderful library of the 1700’s painted by Pannini, who is considered one of the most famous painters of his time. Behind the church rises the beautiful romanesque style campanile of the XII century.