Does the pivotal scene of your genre-defying action adventure take place in your own living room? No? General Kill McKillian doesn't face off against Bigg Meatchest on your suburban patio for the fate of the Underverse?
"And so, Meatchest, we meet again. And how fitting that our final showdown should occur where it all began -- by the lawn chairs!"
Then you need to research location. If you can't personally visit every place you write about in your fiction, see if you can contact somebody who has. Ask them questions. Look up as many photos as you can -- hell, we have Google Maps Street View now! That's no substitute for reality, of course, but it's a big one-up on turn-of-the-century authors who had to tie a wig on the cat, squint at the garden, and pretend it was Africa. The point is, if you're stuck staring at a blank page, the important question to ask is: Why is this page blank? You should have reams of research, notes, and images all there waiting for you -- even if you're imagining an entirely new location.