This is the funeral monument of the Norman hero of the First Crusade, Marco Boemondo d’Altavilla, Prince of Antiochia, It was built on the year of Boemondo’s death in 1111 and is attached to the external wall of the right arm of the cathedral’s transept.  For the external structure the designers drew from the accomplishments of Boemondo during the Crusades, since the mausoleum bears resemblance to the small chapel over the Holy Sepulcher in Jerusalem. The structure is divided in two parts: The one on the top  is characterized by a polygonal “drum” that  nowadays is covered by a small hemispheric dome, and the main body of the monument is of quadrangular shape with a small apse on the right, covered by  salvaged Greek marble slabs and decorated by blind arches and pilaster strips. The inside could be accessed by a bronze door built at the end of the 11th century by Ruggero, a bronze fabricator from Melfi. The inside of the mausoleum is nowadays quite bare due to the constant restoration. The only decorative elements are the two big support columns and the slab in the pavement that covers Boemondo’s tomb which has the following inscription: 'BOAMUNDUS' in a refined setting.