The Basilica of Saint Denis is generally cited as the first truly Gothic building, however the distinction is best reserved for the choir, of which the ambulatory remains intact. Noyon Cathedral, also in France, saw the earliest completion of a rebuilding of an entire cathedral in the new style from 1150 to 1231. While using all those features that came to be known as Gothic, including pointed arches, flying buttresses and ribbed vaulting, the builders continued to employ many of the features and much of the character of Romanesque architecture including round-headed arch throughout the building, varying the shape to pointed where it was functionally practical to do so.
What is considered the first truly Gothic building?
The Basilica of Saint Denis