I hope people aren't sleeping on this series. It's fantastic. You just need to accept subtitles, because it's a German show. But if you're in mood for some dark time travel mystery stuff, it's great.
I absolutely loved the First Season. I was (am) a complete nerd with an open excel spreadsheet with the different time-periods and stuff. I have not watched the Second Season as yet and now the Third Season is out. I may just have to skim the First Season again to get back into the swing of things.
Subtitles are not issue. Finding Time for Time Travel series is the only issue.