Charlemagne, also known as Charles the Great or Charles I, was a medieval ruler and the emperor of most of Western Europe. He is considered one of the most influential and powerful leaders in European history and is often referred to as the "Father of Europe" by historians. During his reign, Charlemagne implemented numerous laws to maintain social order and promote education. He also oversaw the construction of churches and palaces, many of which still stand today. His primary focus, however, was to unite Western Europe as it had been during the Roman Empire. By the time of his death, Charlemagne had expanded his empire significantly, encompassing modern-day France, Belgium, the Netherlands, Germany, Luxembourg, Switzerland, Austria, northern Spain, and northern Italy. The center of his empire was Aachen, a city in western Germany near the modern Belgian border. There, he constructed a grand palace and a remarkable church, now known as Aachen Cathedral, which is regarded as one of the most significant historic buildings in the world. At the time of Charlemagne’s death, his Frankish Empire rivaled the Byzantine Empire in size and was the largest European empire since the fall of ancient Rome.