The album, Days of Future Passed, is brilliant. Easily one of my favorite albums of all time. The album's concept is to take you through one day. From early morning to late night, with the ability to repeat the entire album, and thus see the passage of time into the next day.
Here's a youtube link of the whole thing (if anyone is interested):
It's one of the first albums (like The Beach Boys' Pet Sounds, The Beatles' Sgt. Pepper's Lonely Hearts Club Band and The Zombies' Odessey and Oracle) to hint at what would become progressive rock.