The transept arms, built in about the mid-12th century, have apsidal ends, a feature borrowed in all probability from certain Rhenish churches.

A UNESCO World Heritage Site granted because it is "distinguished by a Romanesque nave of extraordinary dimensions, a wealth of sculpture on its capitals and a transept topped by five towers, all precursors of the Gothic style." In 1243 Bishop Gautier de Marvis undertook to rebuild the choir. When the new work was consecrated in 1255, it still lacked vaults and flying buttresses. This is in a Gothic (Rayonnant) style as is the rose window.