The vault was added by Bishop Nykke, and was necessitated by a fire in 1509, which consumed the wooden roofs of both transepts. During the recent works the small arcading immediately under the line of the vault was discovered walled up, the builders of the later vault in all probability having done this, as in many cases the line of the vault cuts over the arcading. This was opened up, and is distinctively interesting in helping to reconstruct the original finish to the Norman work under the roof. #The Tower and Triforium Walks#, to which access is gained by a staircase in the east wall of north transept, are of much interest. In the triforium the imposition of the later work on the Norman is clearly noticeable, and the original Norman triple windows walled up with the wall shafts which once supported the semi-arches of the triforium roof. Some of the best views of the interior are to be gained from the triforium and clerestory paths. #Interior of Tower.#--A continuation of the same staircase leads to the clerestory, and from thence access is gained to the tower galleries. Above the arches of the crossing there is a vaulted passage in the thickness of the tower walls, with six arches pierced in the inner wall, so that the parts of the interior can be seen from this walk. Above occurs a smaller wall arcade, stopped before reaching the angle to admit of large circular holes being deeply recessed in the walls; and above this again another vaulted gallery, with three windows on either side, pierced through the tower. In the lower of these walks openings occur through the thickness of the walls into the presbytery, the nave, and transepts, just under the vaults, and interestingly quaint peeps can be gained through them. The #Processional Path#, or aisles to the presbytery, consists of four bays to the north and south, with quadri-partite vaulting, with a similar five following round the line of the apse. A door in the north aisle leads out into the gardens of the bishop's palace, and from thence the exterior of this part of the cathedral is best seen.