La Conciergerie is a former palace and prison which is located to the west of Île de la Cité, not far from the Notre Dame cathedral. The building of La Conciergerie was built in gothic architecture, a style that was quite famous in that era.
La Conciergerie does not stand alone. It is actually a part of a bigger tourist attraction called Palais de Justice, a government building which is used for judicial purposes. Tourists come to this site to see the prison which serves as a witness of French history. It was in this prison hundreds of prisoners with guillotine sentence were incarcerated.