Amphitheaters and places with a stage don't get much in the way of large tours anymore because most of those stages can't support most artist's stage.
Except some country and rock bands. I saw Maroon 5 at the Universal Amphitheater (which is actually enclosed and very nice now) last year.
I hate to tell ya, but I wouldn't be suprised AT ALL to see the amphitheaters at all the 'former' Paramount Parks bulldozed. But look on the bright side, how many coasters and rides could they fit there...
