The Museum of the Holy Inquisition is Guanajuato at its darker, more theatrical edge: dungeons, torture devices, and guided visits that lean into the atmosphere. It is not the city's deepest history museum, but it does fit the town's taste for legends, underground spaces, and macabre stories.
Go if you enjoy grim local museums and can take the staging with a pinch of salt. For a fuller sense of Guanajuato's history, balance it with the Alhóndiga, the old churches, and the mining sites above town.