Your favorite 'concept' album

I'm not a concept album fan, however there are a few I've gone down the rabbit hole with. My personal fave, is '10,000 Years' by The Honeydogs. The backstory & lyrics are so vivid, and futuristic, it never fails to reveal something new to me. Even the bandleader said at times he's not sure what it's about.

Fascinating info & interview in the url. Check it out! 

Any others? 
I forgot to mention the truly excellent Blue Sky Mining by Midnight Oil. A very special and moving work.
Pink Floyd - The Wall, DSOM, wish you were here 
Rush - 2112, Farewell to Kings
Moody Blues - Days of future past
The Who- Tommy
Rick Wakeman - six wives

I haven't seen my favorite mentioned yet, so here goes...
Genesis- The Lamb Lies Down On Broadway

Also as others have mentioned:

ELP- Pictures at an Exhibition
Supertramp-Crime of the Century
Any Floyd released inclusive between Meddle and The Wall
Greendale (underrated Neil Young album)
Terrapin Station
Days of Future Passed
Elton John, Captain Fantastic and the Brown Dirt Cowboy! Depicts the journey of one of the greatest song writing partnerships of our pop culture.