I highly recommend these two:
1. Babylon Berlin - Set in 1920s-1930s Berlin, involves a young ‘shell shocked’ German veteran who is a Berlin homicide detective. He has to solve murder cases in the swirling violent politics of Monarchists-Rightists-Early Nazis-Socialists-Communists of Berlin and nihilist Cabaret culture of Berlin. He has his own crumbling personal life - PTSD & drug addiction from the war. Amidst all that he tries to maintain his honor and perform as a dedicated policeman. The show his real historic figures mingled in with the fictional characters. For example, one of his police superiors is the founder of serial killer profiling as a criminal forensic technique. In German with English subtitles, it’s so good you don’t care.
2. Nicolas La Floch - Set in Paris in the late 1700s. Monsieur La Floch is a police inspector in service to the King’s police. It’s set roughly at the end of the American Revolution but before the French Revolution. He has murders, international and court intrigue to deal with as well as trying to operate honestly in a crumbling corrupt royal court environment. It too has several real historic figures weaved in with storyline. His boss was the real superintendent of the royal police and escaped the revolution by fleeing to Spain. In French with English subtitles. It’s also so good you don’t care!
Neither of these are for the faint of heart. Both show the seamy underworld of 1920s Berlin and 1780s Paris and the violence particularly in the La Floch series of pre-modern police techniques.
Pinging myself for later!