sentences:  From the 4th century on, however, the site was occupied by Christian buildings, including a square edifice known as the "oldest cathedral" that was commissioned by Maternus, the first bishop of Cologne.A free-standing baptistery dating back to the 7th century was located at the east end of the present cathedral but was demolished in the 9th century to build the second cathedral.During excavations of the present cathedral, graves were discovered in the location of the oldest portion of the building; including that of a boy that was richly adorned with grave goods and another of a woman, popularly thought to be Wisigard.