This is the oldest part of the cathedral, some of which dates back to before the ninth century. The Saint Lubin [M 005 / crypt], built in the time when Lubin was Bishop of Chartres in the mid-ninth century, rests against a wall which is even older, possibly having survived the destruction of the earlier churches.
Between 1020 and 1024, a much larger crypt was built around the Lubin Crypt by Fulbert as the base for his new church. There are seven chapels in the Crypt, three with barrel vaulting and four with [G 35 / ogival vaulting]. The rest of the vaulting in the crypt consists of groin vaulting.
The ancient well of the Saints-Forts which dates from Roman times is located in the crypt and legends tell of Druidic rituals performed there. Early Christian pilgrims are also said to have visited the well to drink its healing waters.
