Opening in 1991 under its original name of the Riverport Amphitheatre, this outdoor venue was well on its way to being successful at first, but it didn’t take long before “Riverport Amphitheatre” became synonymous with infamy thanks to the now-famous “Riverport Riot,” a free-for-all that started in the middle of a Guns N’ Roses concert by none other than Axl Rose himself. The History of the Hollywood Casino Amphitheatre With a capacity of 20,000 and a sometimes rocky but always rocking history, the Hollywood Casino Amphitheatre has been in the thick of it for almost thirty years. Louis suburb of Maryland Heights, Missouri, just a stone’s throw from the Missouri River, there’s a heck of an outdoor concert pavilion.