I'm not sure, but I don't think I ever got to Physical Graffiti back in the days when I listened to Led Zeppelin. Anyway, it is immense. With more distance from the rock music that dominated my own formative years (which I still, of course, love), it's easier to hear how powerful and great Led Zeppelin were, laying this stuff down before I was born. This is the one with "Kashmir", and a terrific opening one-two of "Custard Pie" and "The Rover" besides.