With Valve's breakout video games, Portal and Portal 2, attracting so much attention as of late, it's easy to forget that portals are something of a time-honored tradition in science fiction and fantasy. So, in the spirit of inclusiveness, we've reached outside the orange box to bring you this collection of concept art, fan art, and stills from some of our favorite windows in time and space.

Remember, we're talking portals here – seamless passageways between time, space, and other worlds. Ofelia's chalk door in Pan's Labyrinth? Yes. Jeff Goldblum's telepod in The Fly? No. Now discuss!

Top image is "Steampunk Portal" by Risachantag at deviantART