Holodeck (joking =P)
Hmmm...besides Arena and Coliseum (which I like, but could be percieved negatively as a place of galaditoral combat between superbeings by 'the press')...
Lightscape, Holoscape, Virtualscape, Hyperscape, Holochamber, Hyperchamber, Holodome, Hyperdome, Hyperzone, Virtualzone, Ground Zero, Virtuality.