Peaky Blinders, Season 1

The gist, courtesy of IMDB:

A gangster family epic set in 1919 Birmingham, England and centered on a gang who sew razor blades in the peaks of their caps, and their fierce boss Tommy Shelby, who means to move up in the world.

If there’s one thing this series does exceptionally well, it’s building a believable atmosphere. Perfomances from the main cast are great, too.