Karlsruhe is Germany's "Residence of Law." The Federal Constitutional Court (Bundesverfassungsgericht) and the Federal Court of Justice (Bundesgerichtshof) are both headquartered here — an unusual concentration of judicial power in a city of 300,000 people. The Constitutional Court in particular is one of the most powerful courts in the world: its rulings are final, binding, and have overturned acts of the German parliament on multiple occasions.
The court buildings are working institutions, not museums, but the Constitutional Court runs a visitor centre and guided tours on certain days — worth booking if you have a legal or political interest. The nearby Platz der Grundrechte, with its 19 pillars inscribed with Germany's constitutional rights, makes the abstract language of constitutional law visible and is a natural companion to a visit to the court buildings.