Your first obstacle: a door. The solution? A cube that's definitely out of reach.
Where is the cube?
At the other end of the corridor, on top of a big portal-proof pillar.
What do I do?
The pillar is portal-proof, but the rest of the room is not. The stairs seemed to disappear when you got up here, too.
Hmm...
A bit of air speed could get you on top of the pillar, but how would you build up enough speed?
Shoot a portal onto the upper part of the wall facing the cube, then shoot another into the pit where the stairs were.
Jump through the latter, and you'll fly towards the cube - ready to open the door and see what's next.
Guide help
This is the low-spoiler guide for "Grabbing the cube" puzzle in Portal. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.
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