Final answer:
The most obvious difference between Cistercian churches such as Notre-Dame at Fontenay and other Romanesque churches is the absence of "ornate decoration". Romanesque churches often feature massive walls, small windows, and decorative elements, while Cistercian churches exhibit an austere simplicity.
Step-by-step explanation:
One of the most obvious differences between Cistercian churches such as Notre-Dame at Fontenay and other Romanesque churches is the absence of "ornate decoration". Romanesque churches are characterized by their massive walls and relatively small windows resulting in dimly lit interiors, however, they often feature decorative elements such as statues and frescos. In contrast, Cistercian architecture, like that seen in Notre-Dame at Fontenay, adopts a more austere approach with much less ornamentation, emphasizing simplicity and the use of light. Gothic cathedrals, which followed the Romanesque period, introduced features like flying buttresses and large stained glass windows, making the buildings appear much lighter and allowing for grander decoration.