The Palais de la Cité, located on the Île de la Cité in the Seine River in the center of Paris, was the residence of the Kings of France from the sixth century until the 14th century. From the 14th century until the French Revolution, it was the headquarters of the French treasury, judicial system and the Parlement of Paris, an assembly of nobles. During the Revolution it served as a courthouse and prison, where Marie Antoinette and other prisoners were held and tried by the Revolutionary Tribunal. The palace was built and rebuilt over the course of six centuries; the site is now largely occupied by the buildings of the 19th century Palais de Justice, but a few important vestiges remain; the medieval lower hall of the Conciergerie, four towers along the Seine, and, mostly important, Sainte-Chapelle, the former chapel of the Palace, masterpiece of Gothic architecture. Both parts of the Conciergerie and Saint-Chapelle are classified as national historical monuments and can be visited, though most of the Palais de Justice is closed to the public.
Archeological excavations have found traces of human habitation on the [Île de la Cité from 5000 BC until the beginning of the Iron Age, but no evidence that the Celtic inhabitants, the Parisii, used the island as their capital. However, after the Romans conquered the Parisii in the first century BC. the island was developed quickly. While the forum and largest part of the Roman town, called Lutetia, was on the left bank, a large temple was located on the east end of the island, where the Cathedral of Notre Dame de Paris is found today. The west end of the island was residential, and was the site of the palace of the Roman prefects, or governors. The palace was a Gallo-Roman fortress surrounded by ramparts. In the year 360 AD, the Roman prefect Julian the Apostate was declared Emperor of Rome by his soldiers while he was resident in the city.