The Casa dos Contos was built in 1782 as the residence and counting-house of João Rodrigues de Macedo, a wealthy tax collector. It is one of the finest civil buildings in the town: thick walls, a quiet inner courtyard, and a heavy strongroom on the ground floor where royal gold tax was weighed before being shipped to Portugal.
The basement still shows the iron rings where enslaved Africans were chained, and the museum is honest about this history rather than smoothing it over. Upstairs are exhibits on the colonial monetary system, including coins, ingots, and the elaborate balances used to test gold purity. Free admission and worth thirty minutes.