Noob question about Garry's mod...

[Big Red Button]

Hey all.
I very recently saw a video someone made about making a fort in Garry's Mod. The place was awesome, it had vehicle hangers, energy doors, a rec room, an armory and tons of neat stuff.
Basically my question is, if when I get half life 2 (which will indeed be very soon) and I download Garry's Mod, will I be able to make gigantic forts like these immediately, or will I need to download other mini mods and such to be able to make these types of maps?

Thanks in advance, and here's the link to the video so you know what I mean:
http://video.google.com/videoplay?docid=-7595407412757907084&q=Garry's+Mod+fort

 

[loadqm]

You'll probably have to download a huge, flat map to build on, but I don't think there's anything else you need, just some practice and patience.

 

[Big Red Button]

Really? Oh that's awesome, I can't wait to build my own massive E-FORT!!!
Thanks.
BTW, did you watch the video?

 

[loadqm]

Really? Oh that's awesome, I can't wait to build my own massive E-FORT!!!
Thanks.
BTW, did you watch the video?

I just watched it now... pretty cool. You might want to get some custom props for building your fort, depending on what you want to build it out of, or what you want inside of it.

 

[Big Red Button]

I just watched it now... pretty cool. You might want to get some custom props for building your fort, depending on what you want to build it out of, or what you want inside of it.

But doesn't Gmod already have every item from both CSS and HL2? I'm sure of all those items I'll be able to find what I want...
BTW, is there actually objects in Gmod for pressing a button and making something blow up?