Amiens Cathedral, Choir, south flank of straight bays

Here you see the aisle windows of the three straight bays of the choir: the great buttress to the right which contains a staircase turret marks the beginning of the turning bays of the eastern hemicycle.
Robert of Luzarches laid out these bays up to the level of the sill of the aisle window in the 1220s: his work ended at the great buttress at the base of the hemicycle.
Characteristic of Gothic design in the 1230s are arches which were no longer as steeply pointed--this can be seen in the aisle windows with their three oculi of identical size, the work of Thomas of Cormont who also built the radiating chapels of the choir. Finally, Thomas's son Renaud was responsible for everything you can see above the aisle roof.
The modern metallic fence is situated roughly on the line of the great defensive wall that ringed the city in Roman times and the early Middle Ages. It was pierced with a gate (known in the Middle Ages as the Porte de l'Arquet)--it was in front of this gate that Saint Martin's encounter with the miraculous beggar is thought to have occurred. This wall was demolished in the decades after the 1180s and a new wall and gate constructed further to the east enclosing land owned by the bishop (the Metz Evêque).