The Romanesque architecture, originating from the modifications of Roman architecture after the fall of the Roman Empire, features thick walls, round arches, and stone vaults, and is prominent across Europe. Characterized by dark interiors and minimal openings for safety, it employed large supports like piers and geometric forms rather than large spaces. Significant structures include the Leaning Tower of Pisa and the Abbey Church of Cluny, reflecting its historical and geographical influences.