Which of the following is NOT a characteristic of Romanesque architecture?

The use of flying buttresses is not characteristic of Romanesque architecture, as this architectural feature is more closely associated with Gothic architecture. Romanesque architecture, which flourished from the 9th to the 12th centuries, primarily features thick walls designed to support the heavy stone structures, along with rounded arches and barrel vaults that create strong, stable ceilings.

In contrast, flying buttresses, which are external supports that transfer the weight of the roof and walls to a distance away from the building, first gained popularity in Gothic architecture to allow for higher walls and larger windows, particularly stained glass. The symmetry in design is present in both Romanesque and Gothic styles, but the distinct characteristic of flying buttresses places the focus on Gothic architecture, making it the correct answer in this context.