I'm watching video entitled "Paul Van Dyk - Live @ Innercity.avi".... I don't know the year, but based upon some tracks I recognize (PvD - Another Way, Goldenscan - Sunrise), I'm guessing it's 1999 or 2000.

At one point, there's a male in a thong and a nude female pole-dancing on stage. What the hell is this?

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D.Squared - The Groove Supremum (December 2010)
D.Squared - New Originals (mix of famous sample sources)

It was Innercity 2000

Female dancers we're kewl, nude all the way
Stagedancers are always at parties here in Holland

yep they own!
there were always strippers at hardcore parties back in the old days