The present cathedral was undertaken by Archbishop Guichard (1165-80), and in its foundation walls were incorporated some of the polished stones from the forum of Trajan, hallowed by the martyrs' blood. So thick were the apse walls made that flying buttresses were never needed. The windows were set in deep embrasures. The absence of an ambulatory, and the flat roof, are reminders that this city neighbors the Midi. The cathedral's apse, as seen from across the Saône, is admirable. Over the arms of the transept are towers whose breadth indicates that the tower of St. Martin d'Ainay created a school in the district. In comparison with the transept towers, the western belfries of the cathedral appear meager. The nave of Lyons rises twenty-five feet above the choir, and, furthermore, is covered by an inappropriate high-pitched roof. Within the church, the difference in height between the two main parts has been gracefully veiled by piercing, in the flat wall over the triumphal arch of the choir, a rose window and two lancets. In size this church may be modest, but its sincere, grave dignity is such that the impression conveyed is that of a very great cathedral. The nave derived from the north. The choir emanated from the south, and its creamy, sculptured marbles and Greco-Italian incrustations compose an interior of sober elegance, the peer of any sanctuary in the land. A unique feature in France is Lyons' incrustations--patterns cut in white marble and filled in with a reddish-brown cement--found only here and in the cathedral of Vienne.[161] St. Sophia in Constantinople first used the decoration, which was imported into Italy and thence passed up the Rhone. The choir of Lyons' Cathedral, up to its vault-springing, is Romanesque, of the Burgundian and Provençal type. The classic pilaster strips are channeled; on each arm of the transept is an apsidal chapel. The prelate who began it, Guichard, had, while abbot of Pontigny, been the host of St. Thomas Becket, and in Pontigny's church he was buried in 1180. His successor, Jean de Bellesmaine (1180-93), born in Canterbury, was another of Becket's friends, and soon after he was transferred here from the see of Poitiers, then under English rule, he inspired the building of a collegiate church dedicated to the new English saint. Archbishop John undertook the second campaign of works on Lyons' choir, which was now vaulted in the Gothic way. On the capitals of the upper walls are the familiar crockets of the north.