This 18th-century treasury building still retains its historic foundry, where gold was melted down and formed into bars under the watchful eye of the Portuguese crown. It doubled as a prison for members of the Inconfidência. The renovated mansion now houses informational displays about the history of money in Brazil. The grand rooms upstairs command sweeping views over Ouro Prêto's streets, while the dank, cobblestoned former senzala (slave quarters) below exhibits harrowing instruments of imprisonment and torture.