The primary trait of Romanesque architecture, and how it received its name, was the frequent use of barrel and groin vaults, two ancient Roman innovations. A barrel vault is a vaulted ceiling that is essentially an extended arch. With their development of concrete, ancient Romans were able to pioneer this architectural technique, and the Romanesque builders revived it in the 10th to the 12th centuries. Groin vaults are made by intersecting two barrel vaults at a right angle, forming a square-shaped vaulted ceiling.
The construction materials are one difference between Romanesque and ancient Roman architecture. Whereas most ancient Roman buildings were made of newly developed concrete, the primary material used in Romanesque architecture was stone. In Italy, where architecture tended to be more diverse in style, some churches built in the Romanesque period had wooden roofs.
Another trait indicative of Romanesque architecture was stone relief sculpture, especially on the walls of churches built in France and northern Spain. Relief is a type of sculpture where figures appear to rise emerge from a flat surface. After falling out of favor in the early Middle Ages, stone relief sculpture became popular again in the Romanesque period. Depictions of biblical figures, especially Jesus Christ, decorated both the interior and exterior of churches during this period.
The semicircular arch was a feature indicative of Romanesque architecture. In both doorways and windows, arches almost always appeared rounded and circular at the top rather than the more decorative pointy-topped arch seen in Islamic or Eastern architecture. This trait was common to almost all Romanesque architecture found in Europe, whether in France, Italy or England.