Depends on the event your attending. They close down as soon as they can vacate the event space being used
Just like Richard Finley said unless you work there --- It's a Denver City Public Facility just like the Airport ( D I A ) for example and is open 24 / 7 with plenty Security !!!
The Convention Center is not a public building. It is only open during contracted hours determined by event managers and then only certain door are open. 24 hour access is through security but you I have to have a reason for being there.
Would really depend on day and event.
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