The friars began building their own church as early as the 14th century. This was a simple structure with a single nave, some elements of which still survive, such as the vaulted roof, now concealed behind the present ceiling and, below ground, the crypt and its impressive murals. Around the turn of the 16th century the friars added a heptagonal choir with Gothic pointed arches and a South aisle. This building phase also saw the addition of another aisle lined with private chapels paid by the wealthy families of the urban patriciate. Their family coats of arms can still be seen today, held by angels. Like many other ecclesiastical buildings, the friary suffered in the Protestant iconoclasm of the 1560’s (the Beeldenstorm),  as can be seen from the damage caused to the grave stone of Antoon van Hille, a counselor to Philip II of Spain.