Throughout history, cathedrals have gone through several changes in order to become what it looks like today. Cathedrals during the Romanesque period and Gothic period stand out in architectural history. Many factors play an influence on how the architecture of these cathedrals came to be. Two Cathedrals, The Cathedral of Saint James (c. 1078-1122) sculpted by Maestro Esteban during the Romanesque period and Abbey Church of Saint-Denis (1140-1264) under the guidance of Abbot Suger during the Gothic period clearly reflects how influences of the time period, technological advances, and culture made an impact on its incredible structure. This paper will employ close visual analysis of two cathedrals, arguing that the inspiration that guided the design plays a heavy influence on how it came to be. Around 800 AD, Romanesque architecture developed and was prominent through 1200 AD. At this time, Romanesque architecture blended influences Europeans had seen during the Crusades. Although many structure types developed during the Romanesque period, the three primary structures were cathedrals, castles, and monasteries. All of which were large and imposing structures used as fortifications and for worship. Romanesque architecture was meant to be large, partially the result of monasticism, a movement in which members of religious groups like monks lived and worshiped apart from the general population. As religious orders grew in size, they needed larger structures to contain them. At the same time, Europe still faced threats from outside invaders, so monasteries doubled as defensive structures. As a result, Romanesque buildings often resembled a fortress, with stone barrel vaults instead of timber roofs. According to Spanswick, a vault is an internal support structure composed of a series of connected arches, usually for ceilings. In addition, building interiors were in the shape of crosses with large piers, load bearing wall sections between arches, or columns and thick stone walls with few windows. Entrances featured rounded arches. Above this arcade is a second level of smaller arches, often in pairs with a column between the two. Such structural elements give Romanesque architecture a very earthbound quality.Around 1140, Gothic architecture first developed in France and gradually spread throughout Europe. It grew out of Romanesque architecture, but added several new elements that resulted in larger churches. These larger churches were increased with vertical emphasis. New and improved building techniques resulted in features like the ribbed vault, which was a lighter, balanced style of a vault that reduced ceiling weight and allowed for taller structures. Walls were supported by flying buttresses, freestanding external masonry supports that combined elements of piers and half arches. Gothic churches gradually developed large stained glass windows, including massive circular windows, due to tracery. Tracery was a method of stone supports that were placed between sections or banks of windows. They helped distribute weight while allowing greater height. Windows and doors included pointed arches, and structures often included towers and tapering spires. Massive walls and semi-circular arches were supported by low, thick columns. The new choir built under Suger’s direction formed a double ambulatory with pointed arches and ribbed vaulting (fig.2). This lighter, skeletal design permitted increased elevation and freed the walls from a primary load-bearing capacity, allowing extensive use of stained glass windows in a higher, more spacious, and light-filled interior. In Gothic churches, everything seemed to aim skyward.There are some differences between Romanesque and Gothic cathedrals that make them distinct from one another. For example, Romanesque structures conveyed a sense of heaviness with thick walls and few windows, recalling their sometimes dual role as places of worship and defensive fortifications. Gothic buildings, on the other hand, with their many stained glass windows and thinner walls, grew to staggering heights. Romanesque buildings used rounded arches while Gothic structures favored pointed arches. During the 11th-century, cities expanded and became more valuable due to traders and craftsmen. The center of power shifted from the castles of aristocrats to the cities. This led to people moving from the country to cities. Great Cathedrals were built which had to reflect the power of the city. The entire community took part in their construction by donating money. This period saw an improvement of technical skills, for example, with the fall of the Roman Empire classical buildings, techniques were lost. It also shows that this style derived from the Roman classical style, but was not able to achieve its perfection.