During the last phase of the second building campaign, about 1270, the delicately proportioned lower church was broken up to apply the articulate system of late Gothic.

Tribunes and pier arches were demolished and replaced by high pillars to vault the central nave. At the same time the walls of the aisles were knocked down to make room for chapels between the buttresses. They had to be shallow, because their exterior wall lined up with the extremities of the buttresses. The result was rather monotonous. The master builder tried to render some rhythm to the structure by using gablets above the windows and by erecting high buttresses as a kind of pinnacles. He had seen that solution at the faÁades of the Dominican church in Ghent built between 1240 and 1300 (torn down in 1860). In that church the bays took up the entire height of the church and were therefore slimmer. The aisles of St Nicholas’s church however were not so well proportioned and due to the massive outlines of the church the fanlight was almost invisible. The attempt succeeded better in the western wing. The huge pointed arch window, the windows of the aisles and the blank walls of the chapels made up an impressive unit.

The medieval people were aware of the ill succeeded proportions of the new longitudinal wing. When the southern chapel was changed into a portal, the capacious turrets and a deep niche rendered the tracery windows a more elegant appearance. The southern portal is a fine example of aedicualar architecture and dates from the 14th century, when a wall was put round the cemetery and a special door was needed to take the deceased to their final resting place. "In paradisum deducant te Angeli" it was sang during the funeral ceremony.

Hence, the new door was named ‘the paradise’ and was indeed paradisaically embellished.

The nave’s tympanum was decorated later on with some reliefs from the former St Veerle church. That place of prayer near the castle of the count was destroyed in the religious troubles of the 16th century. Its chapter house was moved to St Nicholas’s church in 1585, where the reliefs were renovated and painted anew. They illustrate the liberation from the original sin by the suffering and death of the Son of God.