Chernobyl. Holy smokes.
Powerful, depressing and uplifting at the same time and well worth a watch.
I avoided this for months, just because it seemed like a morbid subject. It is.
Recommended, but not for the squeamish or faint of heart.
The bio-robot sequence, in the 4th episode, is some of the most riveting television I've ever seen. It's amazing how they took a clip of the real event, and instead of simply replicating it, they place you in it.