Time Arch
Thanks for all the great replies!
School ends for me in a week so I will finally be able to really get working on improving this map and making others.
The falling into the floor bug is caused by the fact that the floor is a displacement. Apparently Portals don't like displacements. If you place a portal anywhere along the wall in the future room it creates a sinkhole in the floor.
And BTW the slanted wall is actually not the intended solution but I left it in as a secondary solution. After seeing how many people think it is the "right" solution I might remove it after all.
I should have instances of the Arches completed by the end of the week and I will continue to update them as I improve aesthetics and functionality.
Please continue to post any ideas/suggestions/bugs you might have! 
AMD Turion 1.6 GHz, 2 gigs RAM, and an ATI RADEON XPRESS 200M
"LOL I Don't Meet Min Specs!"
Made a quick paint mock-up of the kind of time arch style id like to see make an appearance.
The bit at the top is a clock at it could be digital with a date or a normal one then 999999 for destroyed etc. and the red bits are flashing warning lights. Also could be good to have it go back in time to 50's aperture maybe to get gels in the future and elaborate that how you will.
Short but sweet! I really like this concept and I hope that others take it and run with it. In fact, I hope Valve takes notice of this, because this is the kind of idea that could be used as a main plot point and puzzle element in Portal 3 (if they ever make one).
Why not a Stargate at this point. 
The bit at the top is a clock at it could be digital with a date or a normal one then 999999 for destroyed etc. and the red bits are flashing warning lights. Also could be good to have it go back in time to 50's aperture maybe to get gels in the future and elaborate that how you will.
I have some ideas and sketches of what I want it to eventually look like. But I like you clock/timer idea and I might incorporate that into the design.
Over the summer I'm Going to make a chapter worth of maps based around the feedback from this test chamber, and I am definitely redoing the arch to better fit the Aperture Labs theme.(And Old Aperture)
AMD Turion 1.6 GHz, 2 gigs RAM, and an ATI RADEON XPRESS 200M
"LOL I Don't Meet Min Specs!"
I am SOOOOOOOOO freaking jealous that you thought of this. I'm not going to say "thought of this before me" because it probably never would have occurred to me to use a linked_portal_door that way, but I basically shit my pants when I saw how it worked. If you didn't have this game element in lock down, I would be starting on a HUGE project with this concept IMMEDIATELY! I'm gonna go throw up now...
How do I have it "in lock down"? I am going to release instances and you can modify them however you want.
AMD Turion 1.6 GHz, 2 gigs RAM, and an ATI RADEON XPRESS 200M
"LOL I Don't Meet Min Specs!"
Well, I just like to respect another persons work. I know you mentioned earlier you'd release instances of the time portal arch, but you'll be building your own series of these and I wouldn't want to step on your toes. I don't know... maybe I'll try my hand at it anyway. Thanks dude! (p.s. I was really tired when I wrote that... so don't pay too much heed to it, ya know except the part where its awesome.)
You guys realise that people have been thinking of this idea for a long time? I even know someone who has had a working "time travel" map for a month now. Feel free to do a similar thing without emulating this map/paying credit to where it isn't due.
TL;DR The idea isn't original, don't pay tribute to this guy for inventing it)
(I did enjoy the chamber... or more specifically "tech demo")
TL;DR The idea isn't original, don't pay tribute to this guy for inventing it)
(I did enjoy the chamber... or more specifically "tech demo")
Well I'm not paying him tribute for the whole idea of time traveling portal maps, but rather the specific mechanics. I just thought it was a really cool use of the linked portal doors.