The construction of St. Michel's Cathedral, which was built from the first cornerstone in 1017 to the completion of 1080, lasted more than 60 spring and autumn. The church is divided into three parts: the altar, the ear hall and the hall. Since the uneven peaks provide no broad and flat foundation, several buildings have been built along the hillside to make the church on the same level. The cathedral is in the shape of a cross, and the altar, ear hall and the tomb or prayer room under the great temple are actually masterpieces of Roman architecture. The front of the church is a porch with three arches, which overlooks the sea from the platform in front of the door. The church is a combination of Roman and Gothic architecture, the hall is typical of Roman style, its dome opens up to 7 channels, and the arched corridors on both sides have Roman arch windows to ensure the ventilation and lighting of the church. In contrast to the Great Hall, the Gothic three-story round altar, surrounded by a cloister without a prayer room, is a style of church that is very representative in Normandy and was once popular.