Museum Conciergerie in Paris

You're standing by the Conciergerie, on the Île de la Cité, right in the middle of the Seine. Look at the riverside façade on the north side. You'll see four medieval towers in a row. The round one with battlements and a conical roof, furthest from the clock, is the Tour Bonbec, the oldest of the four. Its name means something like 'good talker'. During the Terror the torture chamber was in this tower, and anyone who confessed everything there was a 'bon bec'.