The Canal Museum in Panama City's old quarter is the best city-centre introduction to the canal that reshaped the country. Exhibitions cover the French attempt, the American construction era, the Canal Zone, labour, engineering, sovereignty, and Panama's eventual control of the waterway.
Visit before or after Miraflores and the locks will make more sense. The museum's strength is that it treats the canal as a political and social story, not just an engineering achievement.