By the Crusader period, a cistern under the former basilica was rumoured to have been where Helena had found the True Cross, and began to be venerated as such; the cistern later became the Chapel of the Invention of the Cross, but there is no evidence of the site’s identification before the 11th century, and modern archaeological investigation has now dated the cistern to 11th-century repairs by Monomachos.
William of Tyre, chronicler of the Crusader Kingdom of Jerusalem, reports on the rebuilding of the church in the mid-12th century. The Crusaders investigated the eastern ruins on the site, occasionally excavating through the rubble, and while attempting to reach the cistern, they discovered part of the original ground level of Hadrian’s temple enclosure; they transformed this space into a chapel dedicated to Helena, widening their original excavation tunnel into a proper staircase.
The Crusaders began to refurnish the church in Romanesque style and added a bell tower. These renovations unified the small chapels on the site and were completed during the reign of Queen Melisende in 1149, placing all the holy places under one roof for the first time.
The church became the seat of the first Latin patriarchs and the site of the kingdom’s scriptorium.
