, Finland First known in the early Christian period, in particular North Africa at
Chlef and
Djemila in
Algeria, and
Byzantium at
Saint John Studio in
Constantinople where Christian churches have been built over
mithraea, the mithraeum has often been adapted to serve as a crypt. The famous crypt at
Old St. Peter's Basilica, Rome, developed about the year 600, as a means of affording
pilgrims a view of
Saint Peter's tomb, which lay according to the Roman fashion, directly below the
high altar. The
tomb was made accessible through an underground passageway beneath the
sanctuary from where pilgrims could enter at one stair, pass by the tomb and exit without interrupting the clerical community's service at the altar directly above. The
Visigothic crypt (the Crypt of San Antolín) in
Palencia Cathedral (Spain), was built during the reign of
Wamba to preserve the remains of the martyr
Saint Antoninus of Pamiers, a Visigothic-Gallic nobleman brought from Narbonne to Visigothic Hispania in 672 or 673 by Wamba himself. These are the only remains of the Visigothic cathedral of Palencia. Crypts were introduced into
Frankish church building in the mid-8th century, as a feature of its Romanization. Their popularity then spread more widely in western Europe under
Charlemagne. Examples from this period are most common in the early medieval West, for example in
Burgundy at
Dijon and
Tournus. After the 10th century, the early medieval requirements of a crypt faded, as church officials permitted relics to be held in the main level of the church. By the
Gothic period crypts were rarely built, however
burial vaults continued to be constructed beneath churches and referred to as crypts. ==Burial vaults==