Abbot Suger oversaw renovations to the Abbey Church of St. Denis in 1140, helping establish Gothic architecture. Inspired by mystic beliefs that light held divine power, Suger used pointed arches, ribbed vaulting, and large windows to flood the church interior with radiant light. This new style emphasized immaterial spiritual illumination over material church structure. Suger believed the light elevated worshippers' minds to divine truths. His innovations at St. Denis established characteristics of Gothic cathedrals like Chartres that remain landmarks of medieval architecture.