Yeah you can.
You have to load a save game where you have it, and use the changelevel console line to load a previous map. And then use impulse 101 or whatever.
Actually, I think you use give weapon_physgun (or maybe cannon).
EDIT: I hate it when I post something just after someone else...
Well of course that's all true.
But there is a bit too much trolling in regards to using the search button. Especially for obscure and 'hard to search for threads' which this one may or may not be, as I didn't bother searching either :P
But regardless, I see your point.
I just think it...
If this has been posted before, feel free to delete this.
A search came up with nothing, but it's a little specific and hard to find.
When you're headed through the underground railroad and you enter one of the train cars where an alien and a resistance member are watching tv. I didn't...
I'm guessing it probably took the combine 7 hours to take over earth. Which could be what the mod is about, or maybe the expansion they are soon to announce?
Also, City 17 is clearly not the only city like it.
There's got to be atleast 16 others, but people have expressed this opinion before.
I couldn't disagree more.
I think, for me, the biggest "wow" I saw in the whole game was the 'train ride' in the .. coffin thingy.. in the citadel. There were many other times throughout the game where my jaw literrally dropped. Having said that, I'm not easily impressed.
As far as physics...